Why do you all have to assume he has "autism" or whatever? Why does it always have to come down to "Oh he's mentally unstable, that's why he does what he does"?
Why not just ignore him if you don't want to see his comments? There's even a chrome extension that, with a little modification, will just remove posts that are authored by him.
Just fuckin ignore him, no reason to mock him, explain to him that he's wrong, just say "Ok!!" and move on.