Before I get a "omg fucking religion fag don't believe in g0d!11 <<::&&", I'm not a Saint.
I am Catholic, and I'm not sure what our concept is for gays, but if they are "sex should be of the opposite", I disagree with it. I don't know whether I'm full on if it's a choice or biological, but either way, I think they should still be treated and accepted by God (if there is one, for the atheists).
Actually, let me rephrase that. I have a 99.9% feeling that it is biological, due to the nature of how they act.
The biological (as in, before birth) debate is partially valid, since in some fields of scientists, there's still debates on whether who a person is mentally is destined before birth through genes, or as a product of their environment, but no doubt it's not a choice. People who say that it is a choice are the same type of people who would have though diseases in the 17th century that weren't known about were caused by witchcraft(a la Salem Witch Trials), and that mental disorders like schizophrenia were caused by demonic possession.