You oversimplify. What the APA has said is, if a person comes in to a therapist and says, "I'm having problems with homosexual thoughts" the therapist is supposed to help the person come to grips with the fact that he is gay. This is whether or not the person really wanted help keeping the homosexual thoughts at bay. In other words, the person doesn't need to want to change from straight to gay - the therapist is supposed to help him make that change anyway.
Shalom.
I might have oversimplified a bit, but not too much, I don't think. The point is, why would the psychiatrist assume that the patient was "gay" because they were having homosexual thoughts? For example, many adolescents have such thoughts as a natural process of growing up, but they are not necessarily gay.
What if a gay man came in complaining about heterosexual thoughts? Would the therapist help him come to terms with the fact he was straight? I doubt it.
Where I oversimplified was when I said a patient might come in wanting to change. That sort of explicitness may be a bit rare. Usually people just want help.