It's not my style to write as if I had the exclusive line on the truth, so I tend to "believe" that things "might" or "could be," generally.
You bring up schizophrenia to say that it occurs naturally. Yes, the definition of mental disorder states plainly that some of them do occur naturally. I understand that something is not exempt from being considered a mental disorder just because it is naturally occurring.
Then you repeat that homosexuality is a deviation from biology, but you don't explain what you mean, and wrap it up by suggesting that it's my fault for not understanding the point you still haven't made.
How is homosexuality a deviation from biology?
This seems like the old argument "they can't reproduce." Is that what you're getting at?
Psychology is not like mathematics and is going to be affected by changes in the environment.
An illness is an illness, I suppose, but your own post above makes it plain that a deviation from what society deems acceptable is part of the definition of a mental disorder. If society changes the definition changes.