• Some people think that God doesn't spoke never. The atheists.
• Some people think that God spoke to humans only until Abraham. These are the muslims, disconsidering all the profets after and their prophecies, Jesus, Son of God, the Father, the apostles, saints after them. Rejecting every information about Kingdom of Heaven, staying in the same dark as people from the 4000 years ago, believing instead the tricks of Mohammed.
• Some people think that God spoke to humans only until Moses. They miss-interpret or dis-consider all reveletions after Moses. These are jews.
• Some people think that God spoke to humans until apostle Paul wrote his last letter and apostle John wrote Revelation book. They ignore all the saints after apostles. These are the protestants, the "Sola Scriptura" believers.
• Some people think that God spoke to humans until to holy fathers in 7-th ecumenic council from Nikea, or until around 1054. They ignore all the real saints after this council. These are the catholics.
• Some people think that God spoke to humans until around the first world war, or until 1923. They lost the apostolic way, ignoring all the saints from the last centuries. These are orthodox new-calendarists.
• Some people think that God spoke to humans until nowadays, and He will speak uninterrupted until the end of the world, as the loving Father. Who are these people?!

• If you are an atheist, you will think that Sodom and Gomorrah story is a genocide, is not an act of God, and cannot be any acceptable God like this.
• If you are jew or muslim, you will think that what happened to Sodom and Gomorrah, was an act of justice.
• If you are a protestant, you will understand that what happened to Sodom and Gomorrah, was a logic act of the God.
• If you are orthodox, keeping with discernment all He revealed to humans in all times, you will know that what happened there was an act of love.

The opinions regarding the narration of Sodom and Gomorrah, as with every biblic narration, variates based on this diversity in receiving of God's revelation.
The different views on this subject comes from the understanding of the subjects: "What is a human?", "What is the purpose of human life?", "Which is the will of God?" .

To answer to these questions, an atheist will consider everything the science has recorded about humanity along the time: medicine, anatomy, astronomy, physics, maths, ... Because he will not perceive anything beyond the 5 human senses and the scientific tools as their extensions (microscope, telescope), the atheist will conclude: Sodom and Gomorrah is a genocide story as other stories from bible.

The muslim and the jew will think: From God is everything: life, death, health, disease, food, starvation, etc. Everything is decided by Him. God is just. So, what happened to Sodom and Gomorrah is an act of justice.

But understanding starts to work, to have some kind of logic, when a human is considered in his integrity as a living being. If the human is composed only from a zillions of cells, that can be seen on microscope, then YES: was a genocid. But if a human has: body, soul and spirit, then NO: what happened there is only a small part of a big picture. Some bodies burned there, but what happend with the souls? What happened with the spirits of these people? What significance has the 2000 years later Resurrection from Death of Jesus Christ, regarding of them? etc...

In Holy Tradition of Orthodoxy is known that God revelated His knowledge to the saints and lets other humans to learn about His revelations from them, by applying in the same time: faith and discernment.

In the year 1389, on June 15, the serbian prince Lazarus died in lost battle against Turkish Emperor Amurat, a battle between christians and muslims. On night before the battle, Lazarus was visited by one of the great angels of the God to offer a choice between an earthly or a Heavenly kingdom. Lazar opted for the Heavenly kingdom, saying immortal words:

"perishable is earthly kingdom, but forever and ever is Kingdom of Heaven!". (orthodoxwiki.org/Lazar_of_Serbia)

Before to die, being in death agony, he start to bend about his choice made in the name of his country, invaded now by muslims. The angel came again and answered to all his questions which torture his soul. One of the question was:

what is the most necessary thing for a man at death's door to ask of his God?

The angel of God answered him:

"At the end and at the beginning of the earthly journey, as well as on every step of that journey, it is most important for the earthly wayfarer to ask God for two things: first, the forgiveness of sins; and second, the bestowal of the Spirit of God. Everything that is full must first be emptied in order for it to be filled. It must be cleaned first, and then adorned. The Spirit of God does not enter a house occupied by a demonic slave of sins, and He does not adorn an unclean home with either His presence or His heavenly gifts."

And then the angel explained to him, and to all humans through Lazar, the complete anatomy of the human, having body, soul and spirit, how important are each of them, which are their roles and component parts they have ... reveling many other mysteries about: proto-parents Adam and Eve, about Heaven, love, superior minds, gold freedom, significance of cross, ... http://tzarlazar.tripod.com/

In this light can be seen that people of the Sodom and Gomorrah, or people from the Noah times, they lost the purpose of their life completely, and decadence or their souls were continuous growing, reversing the values of life from truth to lie, from freedom to slavery, from joy to suffering, from real love to carnal lusts, all these translated in separation of God, ie eternal suffering.

Only in the light of Traditional Orthodoxy, somebody can understand that what happened to Sodom and Gomorrah, or in Noah times, and in all the times, are acts of a loving God. And His love for humanity is overwhelming, cannot be understood entirely or comprised by a human mind.

The Canaanites practiced child sacrifice, temple prostitution, and likely demon worship. The chances are very high that their society was riddled with STDs, violence, and vice. Surely it was merciful for God to cut off such nations. Would anyone want to grow up in a society where they would likely be born with an STD, some of their siblings murdered as "sacrifices" (possibly to demons) by their parents, and violence rampant?

Genesis 18:20-12:

And the LORD said, Because the cry of Sodom and Gomorrah is great, and because their sin is very grievous; I will go down now, and see whether they have done altogether according to the cry of it, which is come unto me; and if not, I will know.

God told Abraham that for the sake of 10 righteous individuals He would not destroy Sodom and Gomorrah.

[edit] I should have also mentioned God's justice, which is rooted in his Holiness.

21 For the upright will inhabit the land, and those with integrity will remain in it, 22 but the wicked will be cut off from the land, and the treacherous will be rooted out of it. Prov. 2:21-22

Death

1. It is God’s prerogative when and how to end life. God needs no reason for this. Death is part of his design; we live, die and are judged. Death is just the means by which we pass from life to judgement.

2. Death is not death; just the beginning of a different sort of life. We might question the circumstances of our death, or our afterlife, but our problem is not with death itself.

3. We do not question God’s justice in people passing away quietly in their sleep after a long life. This shows that we do not find a problem with death itself, but with the manner of our passing.

4. We all know with absolute certainty that we will die. This is a crucial fact of life, which forces us to consider matters of the soul. In other words, death gives perspective to life. -->The boldness of unbelief leaves many men on their deathbed, when they must face their end soberly. Thus, no one has any excuse for being careless with regards to their soul.

Thus, there is no problem with death itself and death fulfills a valuable function, making us consider matters of the soul seriously.

The manner of our passing

Since death is a fact of life and not evil (for God), I would argue that the manner of passing is largely irrelevant. Some pain before passing is not bad – it gives us warning, without which we would be worse off. And no one goes onto a battlefield unaware that they might die violently. One way of dying is more or less like any other.

Genocide

God’s killing of groups of people (himself or through his chosen instruments) is not properly called genocide. These groups are not killed for their ethnicity.

1. Their wickedness is most often cited as the reason for their death; not their skin-color, etc.

2. Their deaths were frequently avoidable, e.g., if they chose not to fight God or his chosen instruments.

3. Some people from among these people were accepted into God’s chosen people, without regard to their ethnicity, e.g., Rehab.

4. Any commands to kill these groups was limited in time and place, for a specific purpose and, so, cannot be related to ethnicity, which is not limited by these things.

Why the killing of women and children?

1. Christian’s interpret the Old Testament as both literal and symbolic; the Jews are a symbol of the church and the individual Christian, and the Amalekites, etc., are symbols of sin.

The Israelites were to give no quarter to sin just as the Church and the Christian must not. They are to root it out big or small, wherever it is found; they are never to mix with it.

1. God is a holy God and is concerned with the absolute purity of his chosen people. This shows us that God does not countenance sin, thus, laying the foundation of man’s need for salvation before a holy God.

2. All God’s purposes relied on the Jews, who preserved the oracles and laws, etc., of God. The Jews were faithless enough on their own, without the influence of outsiders. Hence, God needed to strictly preserve them from these influences. (I might mention, here, the wickedness of the people the Jews were told to fight; how some of them practiced child sacrifice and worshiped petty, savage deities, etc.)

If the Jews had fallen or become faithless, we might never have understood the full significance of Jesus; his life, death, resurrection or teachings.

Alternatives

As to the infinite ways that God might have averted these events, notice,

1. God might have used many ways (e.g., warnings, signs and wonders, previous miraculous victories) which did not ultimately work before using armies.

2. If you are thinking of another way, you might be thinking of some method that would override or thwart people’s freewill. However, this does not generally seem to be part of God’s modus operandi.

3. Ultimately, I would argue that the way God has done it in a way that is better than any of the alternatives. However, without knowing the alternatives, which as you said are infinite, it would be very different to counter all of them!

Generally speaking, the alternatives tend to be the sort of things that children think up, without thought to the consequences and while they may solve a difficulty here or there, they do not fit with God having some sort of coherent, overarching plan. (i.e., they make God a bumbler.)

If you're going to call God's methods "cruel and barbaric," what alternative do you propose, keeping in mind that mankind's free will is held sacrosanct even by God?

It makes more sense when you have an understanding of the plan instead of simply viewing isolated events out of context. God wishes for all mankind to find salvation (1 Timothy 2:4) And when even the worst of civilizations turn unto God, they can turn away his wrath. See Jonah chapter 3 for an example. Nineveh was condemned to the same fate as Sodom and Gomorrah, and they even had a ticking doomsday clock: "Yet forty days, and Nineveh shall be overthrown." But when presented with the prophecy of their destruction, they managed to avert it through sincere repentance.

The second half of verse 8 is particularly interesting: "yea, let them turn every one from his evil way, and from the violence that is in their hands." An abundance of violence is specifically cited (twice) as the reason why God sent the Flood. (Genesis 6: 11-13) Such an attitude is, of course, in direct opposition to the nature of Christ, who is called the Prince of Peace.

So we see that, although it's possible to avert this fate even well into the endgame, as was the case for Nineveh, (see also Sodom and Gomorrah, where God was willing to hold back for the sake of 10 righteous citizens, but even that paltry number could not be found!) when a civilization has turned away completely from seeking salvation and seeking to emulate God and follow his commandments, and becomes filled with violence or other sinful attributes that are in opposition to the nature of God, then they have failed. It's God's wish that all may find salvation, but when a group of people willingly place themselves in opposition to everything that leads to salvation, there's no good purpose to be served by keeping them around, and a lot of harm that they could do if allowed to remain. (Being full of violence means they'd likely go around causing harm to righteous people. Also, they could have children who would be raised in an environment in which they had zero chance of attaining salvation.)

When viewed with an eternal perspective in mind instead of a mortal one, we see these acts of divine destruction for what they are: damage control. Not "wrath" or petty "cruelty and barbarism," but decisive action to prevent harm to innocents.

Egyptians were killing all male babies, not just the first born.

The king of Egypt told the Hebrew midwives, one of whom was called Shiphrah and the other Puah, "When you act as midwives for the Hebrew women, look on the birthstool: if it is a boy, kill him; but if it is a girl, she may live."

Exodus 2:15-16 (NABRE)

And the story of the flood is one common to many, many Mesopotamian religions. See Gilgamesh

and in both stories, God is relenting and merciful in His judgement. He either puts it off till the last possible moment or He finds some good man to carry on His covenant when He would rather have just wiped out all of humanity.

So the LORD said: I will wipe out from the earth the human beings I have created, and not only the human beings, but also the animals and the crawling things and the birds of the air, for I regret that I made them

Genesis 6:7 (NABRE)

So, I think the best way around this conundrum is to

1. Remember that His ways are not our ways. (Isaiah 55:8-9)
2. Recall that the measure by which you measure will be measured against you. (Matthew 7:2)
3. Know that God shows partiality towards no one. (Job 34:19)

This answer draws heavily on The God I Don't Understand by Christopher J. H. Wright. Part II specifically asks "What about the Canaanites?", but the answer addresses the bigger issue as well. He suggests the following improper approaches, which he labels as:

Dead Ends

1. "It's an Old Testament problem which the New Testament puts right"

   The trouble with this approach is that it's a problem in the Old Testament too (God has always been a God of love) and the New Testament does not seem to stand against Old Testament stories. In fact, our doctrines of punishment of sin and the wrath of God are largely fleshed out in the Christian texts, not the Jewish ones. Jesus expounded on the doctrine of hell more than any other Biblical figure.

2. "The Israelites thought it was what God commanded, but they were wrong"

   According to Dr. Wright, the conquest of Canaan was never labeled as a mistake in the Bible, but is "anticipated, commanded, achieved, and remembered as something that accomplished God's will."

3. "It is all meant as an allegory of spiritual warfare"

   Whether or not this view is correct, actual people died and violence was committed against them. It might help us to sleep better, but it doesn't take away the pain, suffering and loss of life.

Next he suggests directions that might not provide a satisfactory answer, but do give us a way to think more accurately about God's actions. He calls these:

Frameworks

1. "The Framework of the Old Testament Story"

   In the Ancient Near East, boasts of the complete extermination of entire peoples were common. However, the boasts were usually overblown—at least if you expect it to mean genocide or "ethnic cleansing". Generally, the boast simply meant the people's strongholds and cities were destroyed. More specifically, the Hebrew word God used to condemn the various nations was herem, which can be translated ban. It meant that everything attacked in battle was to be dedicated to God and therefore burned or destroyed. The Israelites could not profit from these conflict either so as acknowledgement of God's role in the victory or to avoid contamination by foreign gods (or both). In any case, the destruction was limited to specific events and there have been no new commands from God to herem a people since the time of Joshua.

2. "The Framework of God's sovereign justice"

   According to this view, the Canaanites were particularly wicked in culture and religion. Genesis 15:16, for instance, makes a cryptic remark about Abram's offspring not returning to the promised land until the iniquity of the Amorites is complete. It wasn't that the Israelites were particularly righteous. In fact they functioned in part as God's tool of correction, just as God used the Assyrians and the Babylonians as punishment for the sins of Israel later on.

3. "The Framework of God's plan of salvation"

   Dr. Wright points out that God's ultimate plan is to bring peace to the nations. If you think of Yahweh as a god bent on destruction, it's somewhat surprising that He does not allow David, who finally established the Kingdom of the Hebrews with military might, to build His temple. He specifically calls out the blood on David's hands as the reason David can't build the temple. Over and over, the Bible says the one of God's goals with Israel (and the temple) is to bless the nations. Psalm 47 even encourages people everywhere to praise God for putting the nations under Israel's feet. It turns out the Jebusites were not completely eliminated, but over time were integrated into the nation of Israel. Women, such as Rahab, Naomi and Ruth were not only brought into the Hebrew people, but were actually part of the lineages of David and Jesus. Somehow, and it's not clear to me exactly how, God used these violent events to bring about the salvation of all nations.

Summary

I think it's good that we are uncomfortable with the idea that God would use Israel (or anything or anyone else) cause destruction and violence. The Bible is clear, however, that He did consider the destruction of the Canaanites (and the Sodomites and the Egyptians and the pre-deluge peoples) to accomplish His purposes. Dr. Wright's book gives us a few ways to think about the problem that are not completely satisfactory, but at least are Biblical and point us in the right direction.

Remember that God is completely loving, but that he is also completely just.

A truly just God who already decreed that the punishment for sin is death is morally obligated to follow through on that punishment.

As an example, remember in Daniel 6 that Daniel broke the law about praying to any 'god' other than Darius. Despite the fact that Darius liked Daniel, when Daniel [disobeyed], Darius was obligated to throw Daniel into the lions den.

To do any less is to turn God into a liar (something which he by definition is not). He is tautologically constrained by goodness, justice, and omnipotence to act.

Indeed, the real question isn't "Why did God punish these towns (Sodom, the death of the firstborn in Egypt, the inhabitants of Canaan, the world right before the flood)?" but rather, "Why doesn't he wipe out more civilizations?"

Is God merciful ?

The answer to that is his mercy, as evidenced by Jonah.

Jonah, as you will remember, was sent to Ninevah by God to demand they repent. Jonah did his duty, however grudgingly, simply telling telling them "Thirty days and Ninevah shall be destroyed." When Ninevah heard this, however, it repented. As a result, God changed his mind and decided to wipe them out.

That's when Jonah gets upset. Here's what he says in Jonah 4:2:

He prayed to the LORD, O LORD, is this not what I said when I was still at home? That is why I was so quick to flee to Tarshish. I knew that you are a gracious and compassionate God, slow to anger and abounding in love, a God who relents from sending calamity.

In response, God gives Jonah a living parable:

Then the LORD God provided a vine and made it grow up over Jonah to give shade for his head to ease his discomfort, and Jonah was very happy about the vine. But at dawn the next day God provided a worm, which chewed the vine so that it withered. When the sun rose, God provided a scorching east wind, and the sun blazed on Jonah's head so that he grew faint. He wanted to die, and said, It would be better for me to die than to live.

But God said to Jonah, Do you have a right to be angry about the vine? I do, he said. I am angry enough to die. But the LORD said, You have been concerned about this vine, though you did not tend it or make it grow. It sprang up overnight and died overnight. But Nineveh has more than a hundred and twenty thousand people who cannot tell their right hand from their left, and many cattle as well. Should I not be concerned about that great city?

Why does justice demand death ?

Finally, it is reasonable to ask, why should a just God demand death for sin. After all, he is the one who pronounced originally that "in the day you shall eat thereof, you shall surely die." (Here, I'm quoting Gen 2:17. Yes, Romans 6:23 is where I can unequivocally state the wages of sin is death, but I'm trying to stay in chronological order here!)

Here I want to delve into a bit of (hopefully informed) speculation. The Jews understood that one could not look upon God and live. (That's why (a) Jacob was amazed that he wrestled with God and lived, and (b) Moses, who asked to see God's face was told that he could not see it and live, but God did deign to show him his back.)

I don't think it is an unreasonable jump to suggest that when sinful man looks upon a completely holy God, he becomes so aware of his own inferiority that he cannot live with that knowledge. (Its like that feeling of coming back to work after a wonderful Christmas vacation. The shock is killer!)

To look, unfettered upon the face of God, would be to literally die of shame.

Indeed, Dante says that the gates of hell are locked from the inside - Its not that God cannot abide man in heaven, but that sinful man cannot abide God.