I don't really have a take here, but the other day I was watching suicide squad and the big shark dude's entire character boils down to him being strong but intellectually disabled. Is it ok because he's a shark? The underlying joke is still that mental disability is funny. What about big dumb human henchmen in films and cartoons? You know the ones, who go 'uhhhh boss what are we gonna do?' in a 'slow' voice and the boss is like 'get them you imbeciles'...
In the moment the audience and I found it funny, but I never really thought as to why.
At what point does someone go from being stupid to mentally disabled? Why's it ok to make fun of someone for being stupid but not mentally disabled? Neither person can help their mental ability.
Like, I've got a couple friends who are perfectly functional but at school no matter how hard they tried they'd never get good grades. Sometimes they'll say some dumb shit, and people will laugh at them for it.
I think season 1 Patrick from :spongebob-party: is a good example of non-problematic stupidity. He's just less knowledgeable than most people around him and are too lazy to rectify it, confidently living his life with that limited worldview.
Patrick is good because his character is actually funny. "dumb character" is usually just completely boring and predictable.