So you've still not answered my question (or I missed it). What's the difference? Why do we indulge someone's obsession with changing a fundamental issue with themselves, and expecting everyone else to play along...whereas with other mental health issues, we step in and stop their behavior for their own good and we do not play along?
Why the difference?

Why do we interfere with people who have debilitating OCD or Depression? Why do we interfere with people who suffer with suicidal thoughts? Why do we interfere with people who have eating disorders? Are their mental beliefs (their inner self) not just as "legitimate" as the transgendered persons?

On a side note: the concept of "why not do what makes you happy," is probably one of the single most damaging belief structures you can ever have. Why? Because it places a stricture on your life that you must always follow your emotions. That somehow your emotions should reign supreme in your behavior. If I always followed my emotions, I'd be in a very bad place. I very purposefully do not follow my emotions. Why? Because they shift and change from one day to the next. They are stronger or weaker over the long haul. I very purposefully chose to adhere myself to something that I stick to as well as I can....regardless of my emotional state.

~Jeordam