Teachings DO change. To deny this is to deny historical fact. When ideology and facts collide, any reasonable person would change his or her ideology to fit the facts. 

Discriminating on the basis of behavior you deem "sinful" is still discriminating. Like Trid and some others here, you are bigoted against gays,. I deem your discriminatory behavior to be sinful, because I deem all bigotry to be sinful, a far worse sin than some consensual homosexual act. Scripture tells us that the two great commandments are to love God and love our fellow human beings, and you are abjuring that second commandment.

To say that your bigotry is supported by your religion is to pervert the religion you claim to profess.