@9one1,
Depends on what you mean by "choice."
I'm straight. I could certainly choose to live life as a lesbian.
That doesn't meant that I can choose to BE lesbian. I'm going to be attracted to men, and not attracted to women, and that's pretty much that.
Given those parameters, a much saner choice is to go ahead and live my life as a straight person. Which I am.
If someone is bisexual, that's a little different, and there is more choice involved.
If someone is gay, though, it's exactly parallel.