People commonly insult stupidity in creative ways. Many forms of "stupidities" are mental illnesses. While you're changing words around, you're essentially still coincidentally insulting what can be considered disabilities, so in the end does it really make a difference? "Retard" isn't a medical term for quite some time now, it is a pure insult. Medical field now says "intellectual disability".

If I say "stop 'tarding around", is it less insulting? What about saying "intellectually disabled"?

I never use the word myself (EDIT: ... Except now), I just sometimes overthink stuff