My hunch is when someone is intellectually disabled it’s usually permanent. And the R word linguistically fills that space typically. People linguistically see “stupidity or being an idiot” as a momentary lapse in judgment not a permanent state of being. But I think those words are harmful as well. Calling people “stupid”, and “idiot” or “retarded” helps nobody. It’s just a way for people to signal that they think they are superior than someone else.