If someone believes that homosexuality is a choice, that person is gay.
I don't see any other possibility.
Drug use is a choice. Because they do make you feel good. Vegetarianism is a choice, because meat is tasty and convenient.
So homosexuality is only a choice of you want to act on it but choose not to. Even though you want to.
Homosexual activity is only a choice if you ARE homosexual.
Or.... a porn star.
I have no choice to be attracted to men. Or redheads. Even though other people are.