[glouch]

But even a predisposition doesn't determine destiny. You could say that serial killers have genetic predispositions, but they weren't born a killer.

And I've yet to see an objective reason of why it is considered right. (read this knowing that I have nothing against gay people)

True. I think I interpreted the OP's post as meaning that being gay has absolutely nothing to do with genetics, which I don't think is true.