It's a continuum. Sexual libertinism and the destruction of moral absolutes is what is finishing off western civilization. If and when homosexual "marriage" and the elimination of the age of consent (it's in the chute) are legalized (if!), then it will be buh-bye civilized human society and hellooo barbarian totalitarianism!
You're a pessimist. You do know that Periclean Athens was viewed as the cradle of Western Civilization and nascent principles of democracy don't you for about 2500 years? Well, the barbaric Spartans were gay too. The Romans did not seem to be too hung up about gays either. Whatever.