That's blaming the victim. Next you'll be saying people who have been raped are overreacting and "too sensitive" when someone makes a joke about rape. Of course they're going to perceive that negatively, it IS negative. Rape victims relive the terror and helpless feelings of that incident whenever someone makes a cruel and heartless "joke" about it. When autism is used as an insult it makes autistic people feel dehumanized and as if they're at fault for something they can't help being. They don't know, or care, that I've spent evenings crying and miserable and reliving the nightmares I went through before my diagnoses when they said things like autistic people should be killed.
If that makes me too sensitive, well then guilty as charged.
"It's just a joke" is the most stupid and cliche'd internet excuse ever for being cruel and abusive, and people who say that are not needed in this world.
We aren't broken, don't need to be fixed, we are not an incomplete jigsaw puzzle, and we do need to be lit up blue. END. OF. DISCUSSION.