this is gonna turn into a 10 page fun-fest so lemme just say beforehand
call anybody anything you want. call em handicapped, cancerous, socially inept, etc. just remember that when you call someone autistic, if they're not autistic, they're not gonna be offended. when you say "are you autistic?", judging by the rates of autism in the population, they're probably not, and they can just say "no".
stupid is far more viable cus with stupidity, it's totally by your volition that you are stupid.