Actually, it's a little more complicated, like everything we Great Apes do: Some small percentage of people seem to be born bisexual. They are attracted to both sexes. But those people can have exclusively hetero or homosexual relationships, which adds to the confusion around "conversion".

Or there's even the more realistic argument that we are all a little bit bisexual: I'm straight as an arrow, and have never had any sort of relationship with another man, not because of any dislike for gay people. Some of my best friends and relatives are gay or lesbian. But when I see an early Brad Pitt movie, I think: Hmmmmm, maybe I could be with the right guy.