No, I asked you why because the reason it means 'stupid' (colloquially) is because idiots have a longstanding societal tendency to latch on to pyschological terms in order to convey meaning they don't fully understand.

You see this with other terms, like idiots suggesting that a desire to be orderly must be OCD. Or I'm scared of spiders so I have PTSD after finding a black widow.

Look at Rosa's Law, signed into federal law in 2010 in the U.S. The word is officially recognized as a slur, societally and intellectually - at least in the U.S. You use that word to compare someone to a group of people that do not get to choose whether they're mentally challenged. It's degrading and demeaning.

If you wouldn't use the n-word you shouldn't use the r-word.