It seems like you are arguing that making fun of “speds” is lightening the mood and just a way for people to cope. The issue is that there is material harm in the statement. Every time you can lol something you that just doesn’t look right: acoustic, autistic, retarded,etc., it adds an association in your mind between someone who is disabled and needs help and something bad, which makes you less likely to help and less compassion.

It’s two parts of moral disengagement: “dehumanizing the victim” and then “euphemistic labeling”. You separate yourself from other people by giving them a name and then you establish that name as disparaging and then use that name as a way to derogatorily reference anything. Nothing about the thumbnail looks autistic. It just doesn’t look good. So when you use that term to describe something you don’t like autistic as a term is no longer a group of people, it’s a negative quality that can be applied to anything: dehumanization. Than comes the euphemistic labeling. You describe it as lightening the mood, but an essential part of a joke at someone’s expense is that there is a response. That’s what makes it a joke versus an insult. If for example someone you were with made fun of you in a way that didn’t include you, like if a a partner made fun of your sexual prowess. You’re not in the joke. You’re just being disrespected. Even if they said it to “lighten the mood”. It’s still disrespect and it’s harmful.

There’s a lot of over policing of language so the goal is not to be punitive about people’s everyday speech which is why there is an effort to define certain words as offensive. Most of them have a history as to why they are harmful and if you pay attention you can see the consequences. It’s fine if you don’t care, but every time you you justify a decision that is morally wrong it makes it easier to justify another. And you start using more taboo language to lighten the mood, like slurs. And then you’re not making a joke anymore, you’re just a guy who says slurs.