If we're going by historical context (just as we go about TQ+ using queer), those are insults with ableist origin. Dumb used to refer to those who couldn't speak and/or were deaf due to congenital reasons, stupid is based on stupor, idiot is mental/learning disabilities. It's similar to the f-g (used to mean something else before became a slur towards same sex attraction alongside queer). Fool? As far as I know, that isn't ableist and was used for jesters. Although, let's be honest here, I wouldn't be surprised. You got terms like hysterical/hysteria (which some would consider that sexist for justified reasons).

What I'm talking about is that we (as in the sub) seem to very quick to go after TQ+ and their usage of what could be considered slurs (ex queer, although some would say that has been "reclaimed") when we also allow discriminatory language on here to go free. We compare these people and what they do to those with mental disorders. We also use said mental disorders as insults.

• short reply: Basically, we're using mental disorders, something people with disabilities have no control over, as negative connotations to describe the behaviors of TQ+.