How come older civilizations embraced homosexuality and modern ones vehemently rejected it?

I think older civilizations were much more in-tune with the animal nature of human beings and the natural world in general. This is really true of Male Hierarchical order, which is so basic to human Nature that it is undeniable.

As human society “evolved” they added more rules and expectations that have effectively papered over natural human behaviors. The Hierarchy has been one of the victims of this realignment. 

However much they try, they cannot ever destroy it. Men will always respond to Hierarchical order first.