Another example? When I see a YouTube video on men's mental-health or a woman's infidelity, I always see some nut in the comments quoting God, the Bible, or something like those as the reason why it happened; that not adhering to religion was the reason why they strayed. Uh, no, it's just common fucking decency and social norms to not step-out on your partner. Those social norms came from Christianity and their core, but they're not Christian anymore.
And then there is another interesting angle to take on traditional norms normally associated with Christianity - namely, many of them go beyond Christianity. Or even Abrahamic religions in general. Say if we are talking infidelity, were pagan Romans or Chinese or Slavs that different? Sure, they differed in some details, but the general idea that infidelity was bad still applied. Sure, some will dig out some weird stone age tribe from the jungle that is an exception, but as far as most of the more successful civilizations go, there is a surprising amoung of areas in which they share a lot of the same ideas, and that in turn should attract our attention as such independent rising of similar ideas suggests that perhaps the idea in question just simply works, and perhaps it is the people who think otherwise that are the weirdos and let their own beliefs blind them to reality.
While Christian morals mean you can understand and tolerate homosexuality, affirming it isn't possible due to your religious beliefs. Again, that's fine, but most people don't have those barriers: We just see regular people with a different orientation. Being homosexual isn't something that needs to be "locked behind" a proverbial gate to stop degeneracy (e.g. kid-fuckers), but it should be the gate itself: Anything further than that leads down a dark road, as history has shown us many times before.
I think a lot of the controversy around homosexuality is that all the interested parties love to conflate, switch around and maneuver with 3 different aspects of the issue:
1. Homosexual tendencies. Some people have those for some reasons, like it or not, even many conservative Christians go as far as to accept that. But even for them mere existence of that doesn't mean that they should engage in...
2. Homosexual practices. Which are related yet not necessarily strictly connected. There are non-practicing homosexuals (aka exactly what conservative Christians recommend to them), there are also people who engage in homosexual practices even though these aren't necessarily a preference driven by their biological quirks or lack of them (see: prisons, prostitution, certain more exotic cultural practices). Those legitimately raise more controversy than the former, as they may have certain consequences affecting the functioning of the society in various ways, starting with infamous STD spread rates, and continuing with quirks present in the non-preferred examples.
3. Subculture(s) built around homosexuality. The elephant in the room of course being the modern "LGBT movement", with its many symbols, beliefs, sub-subcultures, statistical tendencies in all sorts of areas, and its very demanding, proselytizing attitude towards spreading its beliefs to the rest of society. There are other historical and current subcultures related to homosexuality (like Afghanistan's infamous Bacha Bazi), but i don't think there ever was one with ambitions as widely reaching in influence over host society as the LGBT movement. Even more so than with 2, one does not need to be a homosexual to support those, and neither is anyone under category 1 or 2 forced to support them.
Obviously the most controversy is caused by 3, especially the more radical kind, and more open and widespread cases of 2. Meanwhile some level of 1 and out of sight 2 has existed in pretty much any society historical or current. 3 loves to use that fact to justify everything they want, no matter how damaging, unprecedented or ridiculous. If anyone says they are out of their minds, their go-to move is to accuse the dissenter of being motivated by irrational hatred for people with 1 for something they have no control over.
Dissenters reply that a subculture of merely few percent of society with perhaps a couple dozen percent more loose allies shouldn't get to dictate the whole society how to live and manage its affairs no matter how loud they are and how self-righteous they feel.
Usually chaotic sociopolitical barfight ensues.
So, I'd say it's the former: People decide what is normal and acceptable, with the current non-religious social norms coming from/evolved from an effectively depreciated religion (depreciated in comparison to the massive scale it had been before the pre-20th).
Continuing from the above, unfortunately not just any people, this isn't decided democratically. All sorts of organizations, like religions (western countries being now mixed in that regard means there is no singular religious opinion on many things), social movements, political parties, or really anyone with control over some sort of mass media and a dog in the fight have disproportionate impact on this decision.