You have a choice to be gay, your not forced upon it.
Like straight guys have a choice to be attracted to girls? And have the want to have intercourse with them?
You're born with your brain's hard wiring.
It works both ways. Say your straight and you would PREFER to be attracted to other men. You may 'try' it with other men, but it would feel strange, wrong, and somewhat disgusting.
It's the same way with gays. They can't choose to be straight. If a gay man tries to reproduce with a female, it wouldn't work for him, since he's already attracted to his gender.