And we know this is true, lentulus, because td has told us so. We are outdated because he says so. Our beliefs are disproven because he has told us so.
Oddly enough, when Copernicus disproved the geocentric theory of the solar system, he provided mathematics to prove his position.
Don't ask for proof that homosexuality is not a mental disorder, though. Proof isn't necessary. The thousands of years of history where homosexality was recognized as a mental disorder don't require proof before changing that belief. In fact, you are required to prove that they were right for all those centuries, not the people claiming they were wrong.
Shalom.
Either it isn't necessary, or else a proof one way or the other would prove lethal to the other side's contention that, other things being equal, gay is okay.
For one, homosexuality hasn't been seen as a mental disorder for thousands of years as you claim. In fact, the word 'homosexual' is of fairly recent origin. In many, if not most, cultures in history, homosexuality has co-existed without distinction or particular persecution. You probably already know about ancient Greece.
Secondly, even if it was classified as a mental illness for thousands of years (which it was not), it would have been so based on a faulty presumption, not any "proof".
Your arguments have no validity.