Autism is a gradual thing, not a binary thing. It's not you have it or yo don't there is a whole spectrum of the levels that people exhibit and it can go from being an advantage at times to rendering it impossible for an individual to function normally in our society.

People with a physical disability have a whole lobbying system in place to force society to make room for them, mentally challenged people, by their very nature, do not have anything that compares and likely never will.