Buddha's view on sexuality

Q1: Did the Buddha remain silent on these matters because of a specific reason?

There are several suttas outlining the premises for a healthy partner relationship, according to buddhism. See samajivina sutta for instance: https://www.accesstoinsight.org/tipitaka/an/an04/an04.055.than.html, or sigalovada sutta: https://www.accesstoinsight.org/tipitaka/dn/dn.31.0.nara.html

Q2: Could it be that a majority of Buddha's teaching are timeless, but few are open for change, due to different societal context etc.? (e.g., 3rd precept)

The third precept advice against adultery among other things, but to my understanding the specific actions considered harmful vary with different interpretations of the suttas.

However, if one look beyond the specifics, one could say that the gist of the third precept is to refrain from hurting relationships with sexual actions. Going into specifics of what is prohibited, what is permitted, with who, where or when, risks clouding the purpose of the precept.

I would argue that this principle in its essence is still valid in today's society.

Q3: In the above quote, isn't it a bit biased to state that it's ONLY a woman's taint? Why not a man? Why focus overly on women? Back in those days, there were probably fixed gender roles, but I believe society should progress & should rather acknowledge individuality even among the genders. It seems that the Buddha is over-generalizing, or did the miss the boat?

Are you asking why the suttas doesn't correspond to your values of societys progress, or gender equality? I am not looking to debate these things, but i do wonder why you expect several thousand years old suttas to match contemporary ethics.

In contemporary society sex is mostly seen as something pleasurable

Or not, perhaps it depends on who you ask.

craving to be touched etc

Perhaps, but even in ordinary society there are many, many forms of non-sexual social "contact".

Did the Buddha remain silent

I don't think so. You might like to read Bag of Bones or something like that, the doctrine is all pretty explicitly anti-sensuality -- including the stories of the Buddha's resisting Mara's beautiful daughters, and the beautiful servants in his palace -- it (anti-sex) is explicitly in the Vinaya (the rules of Discipline for all monastics).

Could it be that a majority of Buddha's teaching are timeless, but few are open for change, due to different societal context etc.? (e.g., 3rd precept)

As it happens, yes :-) -- i.e. I think that the 3rd precept changes on Uposatha days when laypeople practice "8 precepts" instead of "5 precepts" (more in this answer) -- perhaps (on Uposatha days) to be more like the Sangha.

In the above quote, isn't it a bit biased to state that it's ONLY a woman's taint? Why not a man?

I too find that strange.

I even questioned that once, here ...

Questioning the translation of AN 8.15, “Misconduct is a woman’s stain”

... asking whether that's really the right translation. I'm told the translation is correct.

If you find it incredible, another possibility is that the text might be "corrupt" i.e. altered.

In an answer to this topic -- Can the Buddha ever be a woman? -- I found a long analysis comparing a sutta to its equivalent agama. That analysis showed -- quite credibly IMO -- that the two were slightly different and that in that case it was the agama which seemed to be the more reliable -- and the sutta had had some "women are inferior" ideology added later.

But who knows.

Some modern sensibility is to be egalitarian, there are limits to how universally true that is (e.g. in all societies).

As far as I can see, Buddha taught extensively to lay people how to treat each other friendly & compassionately, but omitted the bodily intimacy aspect of it.

Correct.

It's largely sensual desire that binds human couples together,

I think the Buddha would disagree with the above. In AN 4.55 and AN 4.53, the Buddha says it is having the same faith (goals), the same morality, the same sacrifice/generosity and the same wisdom that binds human couples together.

Since the 1960s sexual revolution, the amount of sex has enormously increased and the amount of "binding of couples" has enormously decreased. This appears to show that it is not largely sensual desire that binds human couples together.

Historically, it was obviously family, children & religious norms that bound couples together.

Unchastity is the taint in a woman

"Unchastity" is merely a translation of a word (duccarita), which most generally simply means "misconduct". The English word "chastity" can mean "celibacy" (which in Pali is "abrahmacariyā") but it can also mean "the state or practice of refraining from extramarital sexual intercourse", which is what Dhp 242 is obviously referring to.

AN 6.52 says: "Itthī puttādhiṭṭhānā: Women have sons as their support/mainstay". In other words, women should not use sexual intercourse as their support/mainstay or social refuge.

Q2: Could it be that a majority of Buddha's teaching are timeless, but few are open for change, due to different societal context etc.? (e.g., 3rd precept)

No. It is a timeless religious teaching the people should not have extramarital sexual intercourse. Anyone that believes extramarital sexual intercourse is not unwholesome & not harmful and a life-style possibly will not attain the Noble Path. MN 115 refers to what is possible and impossible as says:

They understand: ‘It’s impossible that someone who has engaged in bad conduct of body, speech, and mind, could for that reason alone, when their body breaks up, after death, be reborn in a good place, a heavenly realm.

MN 115

The Buddha taught (DN 31) parents have a duty to arrange the marriage of their children. Therefore, in the 3rd precept, the word "protection" means this, namely, children and particularly a daughter is "protected" by her family until she is married. The Buddhist Commentaries are also very clear about this (which the monk named Yuttadhammo posted somewhere on this forum).

Q3: In the above quote, isn't it a bit biased to state that it's ONLY a woman's taint? Why not a man? Why focus overly on women? Back in those days, there were probably fixed gender roles, but I believe society should progress & should rather acknowledge individuality even among the genders. It seems that the Buddha is over-generalizing, or did the miss the boat?

No. It is not biased at all. The question simply shows a misunderstanding of women and being beguiled/fooled by the modern social engineering or sexual exploitation of women. Women are different to men. Women have wombs and biological & psychological mechanisms created for both child bearing & controlling of families (nest building). There have been many scientific studies done on how sexual promiscuity affects female "bonding" instincts. Unlike men, in my experience, once women veer down the perilous path of sexual immorality or sexual promiscuity it is difficult for them to return to a state of wholesomeness. Women can develop "sexual addiction" in a manner which is a quest to over rejection & regain power. There are many studies & theories on this, such as merely this example: Female Sex Addicts: Using Sex for Power and Control. Even when such women eventually get married & have children, they will generally maintain the wrong views about sex, which they will impart to their children, who are then likely to commit sexual misconduct. Thus relationships in society, which we witness today in the West, often fall apart.

One should be aware, for example, it is reported 25% of Western women, over the age of 40, are using some type of antidepressant. Women are simply not designed by nature for sexual promiscuity because, as the Buddha taught (in AN 6.52), women have the strong tendency towards "domineeringness" and thus, in my experience, they generally struggle to admit wrong doing once they commit wrong doing. If one has any experience with women, one will find they get very angry, very upset & even very shattered when they are accused of serious wrong doing. If one examines Radical Feminism, for example, it will be found Radical Feminism rarely blames women for their problems and generally exclusively blames men for female problems. Any competent psychologist can explain this, such as this video called One Clinical Mistake That Can Heighten a Client’s Shame.

Women are nearly twice as likely as men to be taking the medications, the report found, with antidepressants used by 16.5 percent of females compared to just under 9 percent of males.

WebMD

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Over the past decade, people have increasingly treated depression with medication: Starting in 1994, the number of antidepressant prescriptions written by doctors went up 400% over a 10-year period. And today, about 15% of women take an antidepressant. Among women age 40 to 59, that number is nearly 23%, according to the U.S. Centers for Disease Control and Prevention (CDC).

Woman's Day: Depression is common among American women, and antidepressant use is on the rise. Yet women tend to keep both a secret. Why aren't we discussing this more?

In summary, per MN 115, anyone that believes extramarital non-committed sexual intercourse is a lifestyle possibility will not attain the Noble Path. This is because they will not be free of the hindrance of sexual desire and have insufficient loving-kindness & compassion to empower their practice.

There are two levels of Teaching, for the common people, and for professional seekers of Nirvana.

To first, Buddha taught no-nonsense ethics, chastity etc. Sex for procreation, faithful marriage, these kinds of things. Going mostly by his basic principle of "what leads to peace and harmony is good, what creates causes for potential conflict is bad" - applied to the social norms of those days.

To the second, he taught universal principles operating at cosmic scale. Natural evolution ("dependent origination") emerges as cyclic self-perpetuating tendencies. These self-perpetuating tendencies culminate in arising of sentient experience. Information trapped in these tendencies identifies some elements of this experience as "self". What in reality is a perpetuating part of the tendency (its capacity for continued existence) in sentient experience arises as something subjectively desirable. This includes sexual attraction.

Therefore, breaking through the charm of seemingly pleasant, and correctly attributing its nature to the self-perpetuating tendency for continued existence, is an appropriate component of practice leading to liberation from the trap of subjective experience.