I can't speak to much of this as I am not a classics expert or a Medievalist t, but I'm not sure where you get the idea that Christianity reinforced
class distinctions of all things. In any case, unless we want to play Gibbons, I have a hard time imagining that Christianity contributed to the breakdown of the Roman Empire more than garbage leadership did. A lot of the original post sounds mostly like a mid-2000s anti-Bush/anti-Christian strawman and I'm not sure if it invites any rational response. Linking drug use to "progressiveness" is at least mildly amusing. Bourgeois puritan capitalism was the true progressivism.
I won't address the whole topic right now, but I do have a minor nitpick. I took a class on classical Greek thinking, and this idea that homosexuality was "accepted" (as it is today in much of the world) is really misunderstood. Many intellectuals at their little get togethers did, of course, have homosexual relationships. However, this was a very overthought conclusion to their assumption that women were inferior. Much of their writing talks about how you can't truly LOVE something that is not your equal, so a true experience of love would have to be with a man. This did NOT equate to accepting two people, say two men, in a lifelong relationship. There were plenty of instances of men who wouldn't take a wife and instead took a husband being publicly shamed and even tried for such an offense.
I can't remember if it was Hadrian in Rome or one of his less well-regarded fellow Caesars, but there was one who was the "woman" in the relationship, or declared his lover to be his true spouse or something, to great offense to the Roman body politic.