I have no doubt that a person can change their behavior, whether it's from a genuine desire to change, or a matter of opportunistic convenience (Ann Heche), but one cannot change their sexual orientation.
I recently saw on Court TV a man who had undergone a sort of sexual preference lie detector test (I won't give details, just use your imagination). I'd like to see anyone who claims to be a newly heterosexual ex-gay take one of these tests. The results should be interesting.
Of course, based on research, thhis is false. Orientation is similar to other ual disorders where it takes a lot of work to correct. Maybe look at the research then decide rather than basising your opinion on ignorance and/or emotion.