(is trans-sexuality a psychological feature, too?)
... what does this have to do with the discussion on sexual preference? Transsexuality doesn't really have anything in particular to do with that. Is an issue with gender identification, not sexual preference, so far as I'm aware. Verra' different things.
Separate discussion being such, I do think some areas are beginning to treat trans as a legitimate psychological issue of some sort or another. With appropriate treatment: Gender reconstruction and hormone therapy, after which the person in question is psychologically normal for their (previously misaligned) gender and operates as well as anyone. 'Course, there's plenty of bigots/ignorant individuals up in arms about nationalized medical systems or anything remotely resembling them actually forking out money to fix the issue in question, but what can you do? You've got people that value what they view as "normalcy" over others' health and sanity in every society, s'far as I know.
Still, it is certainly not biologically normal behaviour, and as such should be considered a problem.
And here is kinda' the fundamental problem with the way you're thinking, methinks. Something not being biologically normal behavior (though note: Homosexuality
is biologically normal, by everything I've seen. Relatively low probability, but normal) does not mean it's a problem. It means it's
different, but whether that's an
problem is an entirely separate consideration.
E: But nah, the stronger reason why it's not considered a problem is that homosexuality has no meaningful effect on psychological functioning. It is little-to-no more impactful on how you think and how you function than preferring brunettes over blondes. Has no impact on work ethic, morals, intellectual or physical capability, the vast, vast majority of social interaction... it's a non-harmful sexual preference, and that's
it. Which is why it's not a problem.