What rot! The romans were 'perverse' for several hundred years, the egyptians: Their entire belief structure was about some god wank*ng into his own hand!
And their civilisation is lasted for like 4000 years.
You're implying some sort of moral absolutism here, based on a modern Judaeo Christian belief structure. Ancient peoples did NOT think as we do, what you find morally repugnant does NOT apply to ancient peoples, and quite frankly I am unsure about what evidence you are using here, that there was some sort of massive cultural shift within cultures, to create a cross cultural objective viewpoint. If you think further on, what exactly do you regard as 'fall of civilisation' anyway, since most civilisations break up, splinter, but then form branches and offshoots. Rome, the Vatican, is still the centre of the Holy See, which controls one of the most populous religions in the world!
you really need to look at more history, and try and come up with some actual 'evidence' to validate your statement, scientifically!