Sorry. Dumb hasn't been medical terminology for a long time, and in current usage, anyone can be dumb or do dumb things. I find it liberating to have words to describe bad decisions or faulty reasoning in a non pathological manner. I think we should avoid thinking of people as lesser for lacking certain intelligences, or referring to members of an outgroup as dumb, but trying to get rid of terms like that is not worth the trouble. It's fine to use formally derogatory terms in a self depreciating manner, and people from marginalized groups can even reclaim them.

The term queer has been used as an insult, but I personally believe it's the best term to use when describing members of the LGBTQIA+ community. It encompasses all members of the community, from the most het-passing gay white men to the most flamboyant trans person. It describes the more invisible members of the community, from asexuals to intersex folks. It can even describe GNC cishet people. It basically points out that we are different, atypical, not the norm, but there isn't anything wrong with us.

Terms like the R word are still used in medical contexts, describing delays in normal development. It's being used less and less, with doctors avoiding the term as an official diagnosis. Mostly doctors use the term to describe a specific aspect of the patient, usually intelligence, but not essentialize the patient as that word. However, when it's no longer used in official medical terminology, it'll probably go the way of terms like idiot or dumb. It'll be bad to attack someone by calling them the R word when they might have genuine delays, but when used amongst your in group, it isn't worth splitting hairs over.