When faced with any phenomenon, the logical question to ask is why it is there.
There are many people who see homosexuality as a sin; but the question they never ask is, Why does it exist? There is a body of thought that says that homosexuality has evolved for a reason, and that reason is this: Humanity needs people who won't be having children in order that they focus all their energies on benefiting the species or the tribe.
These questions are also not asked enough in matters of, say, schizophrenia and bipolar. Why do these things exist? I have an explanation why they exist. Just as the species needs people who won't be having children, so it also needs people who think differently from others around them so that they can innovate and so that they see the things that others around them do not see. Just as with homosexuality, which has for much of history been seen as a sin, these things, that are typically seen as mental illness, have survived for as long as they have survived because there is a need for them. And while people who have such adaptations can be disadvantaged in some pursuits, they become highly useful in others.
The people who have these adaptations, like all people, fulfil their part in the human process. What they can see, that others don't see, ends up benefiting the world. Some of the world's greatest inventors, greatest scientists, greatest writers and artists, greatest politicians even, had these supposed disorders. These things have survived for as long as they have survived - because they are necessary.
When everyone thinks the same way, it takes someone with a different mentality to see where they are going wrong. When everyone believes the same thing, it takes someone with a different mentality to see where the beliefs are incomplete. It takes someone who thinks in original ways to invent, to innovate, and to bring new things into manifestation. I would not call these adaptations mental illness. I would call them different modes of mental organization, that like all other forms of mental organization can go for good or for ill.
The people who attack such things are as wrong as are the people who attack homosexuality. We are dealing here with a necessary adaptation. You don't attack a cat for not being a dog, nor do you try to mold a cat into a dog. You see a cat as a cat, a dog as a dog, and recognize that the world is big enough to accommodate both species.
Some will be dogs, and others will be cats. Some will be "normal" and others will be different. There is a need for these adaptations. And the sooner people understand that, the more they will be able to benefit from what people with such adaptations have to give.