Heterosexuality, being the norm, is no more chosen than breathing. Homosexuality, however, is a perverse behavior that is chosen. The desire to commit homosexuality may be caused by some underlying desire to deviate from the norm. Still, having the desire doesn't not mean that one will participate in the behavior since humans are more complex than a simplistic cause-and-effect scenario. All human behavior is chosen. That's what separates us from the animals.
And this makes sense to you?