Homophobia generally spread throughout the world with Christianity, carried by colonialism. Again, China is a good example. And fixing homophobia in western societies strongly corresponds to decreasing importance of religion.

It’s not limited to homophobia of course - pretty much every single Catholic claim about human sexuality is antiscientific bull - but I think homophobia is a good enough example of a harmful, false belief that got more popular than anything post-internet.

For one thing, you may be underselling the homophobia in Islam a bit. And there's Tacitus, who says that the Germans punished homosexuals. That's a bit before the Christians, and it comes from someone from a culture not opposed to the practice.

Second, I find it hard to believe that the Chinese were turned homophobic, and remained so, by a few Christians despite millenia of tolerance, when the vast majority of the country isn't even Christian. It smells like bad historicism.

I guess his take on germanic tribes might have been accurate. The first recorded "law" in the Nordics is monetarily punnishment for accusing someone of being homosexual. (Quoted from distant memory, don't take my word for it).