It is not proven that people are born gay or straight. But it is a possibility.
However even if environment later in life contributes, it is still not a choice. Nobody can choose their sexual orientation because it is not controlled by conscious brain. Choice only comes into it when talking about homosexual sex acts. I dont think it is a sin to be gay, just to act on it.
So yeah, sorry gay people, you have to live a life without sex or you'll go to hell forever. It's not your fault you're this way, and there's actually no harm in it at all, but that doesn't matter to God. He'll judge you for it anyway.
And it's a pretty well supported possibility. It's not "we think it's this, but it could just as well be a choice". It's more "there's a significant amount of scientific data supporting the theory that homosexuality is a result of biology." Don't try to weaken this with the "it's just a theory" argument. It doesn't work for evolution, and it doesn't work for this.
Its nothing new, lots of people have subconscious tendency to be violent or commit other sins, and they were made that way by genetics and childhood environment, by no fault of their own. Are they still responsible for their actions in the eyes of a christian god? What about psychopaths who cannot into morality because their brain is wired that way from childhood, would it be an excuse?
Are we seriously equating "two consenting adults of the same sex sleeping with each other" with "criminal violence and psychopathy"? You've got to be kidding me.
Here's the difference, if you need me to spell it out: one of these things doesn't harm anyone. You get three guesses for which it is.