insideontheoutside: Hmm, actually, I may be mistaken, but I think a transsexual actually seeks and requires (not to "live" in all cases, but to achieve more happiness at least), situational, medical and economical aspects aside, medical treatment to make their body as congruent as possible to the chosen sex/gender, no? Else they would be called "transgendered" without going in the "transsexual" category, wouldn't they?
What I meant is that an homosexual, social stigma aside, theorically, is happy as is and does not require surgery or something. We (most of us, I think, anyway), even if we were allowed to dress as whatever gender we would want to without any social disregard or anything like that, theorically, should still seek transition. Else we would be crossdressers, right? That means we cannot achieve optimal happiness and/or functionality without a medical transition of sort.
This is a phenomenon that has yet to be explained and as individuals affected by it need physicians' attention, at least until they better understand it, I think it's appropriate to call it a disorder. Aren't all things people are born with that greatly affect their lives normally called something like that? I mean, they need a starting point to actually understand things.
If someone were born with a greatly disabling birth defect that cannot be removed without surgery, wouldn't it be some sort of "disorder"?