This is shown by the thousands of men and women who are attracted to the same sex and desperately try not to be. People would never choose to be gay in Iran or Sudan where people are killed for it, yet they exist there anyway. Whether genetic, environmental, or a mix of both it seems fairly obvious it wasn't a choice for them who they were attracted to.
Now I will say that this doesn't prove that it is never a choice, but that at least for some people its not.
There should be Instant Runoff Voting