Actually, there are countless former homosexuals.
So, you are wrong.
If you"re talking about behavior, I believe you. Under that standard there are countless former heterosexuals too...ask about 1/2 the married men you know. They are certainly "former" in the sense they don't get any sex.
The question is, what kind of sex would they choose if they could have any they wanted?
That's my definition of homo and hetero.