I don't have anything else to add that hasn't already been said but I just wanted to say that being adopted or an alcoholic is indeed very painful but entirely different from being gay. I am not saying either is harder or worse but they are different and can't be compared unless you have experienced all three.
I do think it is a therapists job to educate themselves or they have no business claiming to be able to help clients when they have no education in this area. It's dangerous and can be very damaging. This is where ethics come into it and the therapist should no their limitations and refer.