I have actually heard the argument - "If we legalize gay marriage, what's next? Beastiality? Pedophilia? Should we allow people to marry children and animals?"
It's bizarre, but yes - there are people out there who *do* believe that legalizing gay marriage is the first step on the road to ruination of civilization.
I agree with Oniya - look to the plank (in some cases, the whole damn tree) in your own eye, my friend.