I'm not referring to stupid in a sense like having a character quirk. I'm referring to stupid in the sense of "being a hero" with everyone in your universe licking your nuts like you are some kind of hero when in reality, looking at it from an out of universe perspective, you basically allow criminals you capture to kill innocent people later by putting them in the same prison they've broken out of 5,000 times prior, so often to the point where you expect them to break out and kill people later, ad yet you still just drop them off at the same prison once you catch them, like it's a daycare.
That's the type of stupidity I'm referring to, not a cheesy type of stupidity or a Deadpool type of stupidity, it's more of a constant PIS type of stupidity. Now, yes, I agree with you that even that could be something that people just find attractive about the character, which is fine. I don't find it appealing at all though, personally. I think it's annoying that the Joker, some fool with no super powers, is still alive killing innocent people every other Friday because the people in charge of policing him won't do what needs to be done, for fear of "crossing their own line". I like my heroes to act heroic, my anti-heroes to act in a gray area sort of way, and my villains to act like villains. *shrug*