My question is for Biblical Unitarians and is based on their website as it relates to Philippians 2:6-8

Mark 10:18

And as he was setting out on his journey, a man ran up and knelt before him, and asked him, "Holy1 Teacher, what must I do to inherit eternal life?" And Jesus said to him, "Why do you call me holy? No one is holy but God alone.

more even, he was fully aware of the difference:

Matthew 24:34-36

Truly, I say to you, this generation will not pass away till all these things take place. Heaven and earth will pass away, but my words will not pass away. But of that day and hour no one knows, not even the angels of heaven, nor the Son, but the Father only.

and in this it is manifest that in the last sentence he said the truth, as it proven that he did really not know the hour.

The argumentation on the cited Unitarian page is almost as complicated as the Trinity dogma. The reality is that Paul and John tend to attribute a divine quality to Jesus which is the root of the trinity dogma. But Jesus himself had clearly denied because he knew it.

"Here is a clear statement by Paul of the deity of Christ."

If Paul had wanted to make a clear statement equating Jesus with God, he sure did it in a funny way - a series of verses that are highly contentious, whether between trinitarians and unitarians or just between trinitarians themselves.

IMO something clear would have been something that included "Jesus is God." Easy! Because this is an earth-shattering claim for Paul, an observant Jew who believes God is Spirit, you would think he would not only state it once in one letter, but repeat it loudly and clearly. Instead, he uses a word here which can mean all sorts of things ('morphe'), in particular 'shape' or 'outward appearance'.

Strong's Greek 3444: Form, shape, outward appearance. Perhaps from the base of meros; shape; figuratively, nature.

On the other hand, St. Paul distinguishes time and again between Jesus and God. So which is the proper hermeneutic - a cryptic, highly debated sentence which suggests to some that Jesus is God, or clear, repeated statements distinguishing them? My hermeneutic favours the latter.

Philippians 2 5-11:

"Have this mindset in you that was also in Christ Jesus, who, though he was in the form of God, considered being equal with God not something to be grasped, but emptied himself, taking the form of a servant, being born in the likeness of men; and being found in fashion as a man, he humbled himself, becoming obedient to death—even death on a cross! And therefore God raised him to the highest place of honor and gave him the name that is above every name, in order that at the name of Jesus every knee will bow—in heaven and on earth and under the earth — and every tongue will confess that Jesus Christ is Lord, to the glory of God the Father." (Revised English Translation)

(As a sidenote, the passage distinguishes between God and Jesus just after 2:6-8 at 2:9. "And therefore God raised him to the highest place of honor [...]")

The article you linked to explains fairly clearly in what sense Jesus was 'existing' as the 'morphe' (form) of God and instead took on the 'morphe' (form) of a servant:

"Scripture says Christ was the “image of God” (2 Cor. 4:4), and Jesus himself testified that if one had seen him, he had seen the Father. Saying that Christ was in the “form” (outward appearance) of God is simply stating that truth in another way. Unlike Adam, who grasped at being like God (Gen. 3:5), Christ, the Last Adam, “emptied himself” of all his reputation and the things due him as the true child of the King. He lived in the same fashion as other men. He humbled himself to the Word and will of God. He lived by “It is written” and the commands of his Father. He did not “toot his own horn,” but instead called himself “the son of man,” which, in the Aramaic language he spoke, meant “a man.” He trusted God and became obedient, even to a horrible and shameful death on a cross."

On this view, Jesus isn't just a man like any other man. He is the Son of God, the Messiah. So what does 'being made in human likeness' mean? My best guess on this view is that it means he carried himself as a typical man, the 'son of man' - a carpenter from a small-town.

So, from the OP:

"Since Jesus Christ was born as a human being like the rest of us, meaning He appeared as a man why was it necessary for Him to take the form of a bond-servant/man at Philippians 2:8 since He is a man already?"

He is born not just any man, but the Son of God. He has to empty himself of "all his reputation and the things due him" as the Christ, and follow God's plan.

Q: You say St. Paul's language isn't clear here re Jesus' divinity, but isn't he being clear at Titus 2:13?

A: Titus 2:13 is another contentious passage. See here for a Biblical Unitarian discussion of it.

Q: But how could he be born a man if he starts out a man?

A: This question seems to take a trinitarian lens to the passage. So he's in the form of God, then empties himself just before or during the incarnation, and so is born a man. This is not the unitarian view - this is not a temporal sequence referring to conception. St. Paul does not make the logical connections between the various elements clear here, but 'being born in the likeness of men' is probably a paraphrase or goes along with taking the form of a servant - i.e., “emptying himself” of all his reputation and the things due him as the Messiah and Son of God and living in the same fashion as other men. This is probably meant to refer to an on-going state of affairs (hence a 'mindset'), not an event that just happened once as in the trinitarian view.