There’s a clear campaign against the mentally ill with the global rise of fascism. Lots of it shows up in anti homeless rhetoric, but you can see it in the MAHA and anti vaccination movements.
There’s no reason to use the word “r-tarded” to describe someone. As someone who’s worked with the intellectually challenged, it’s an insult to them to compare them with people who are willfully ignorant.
“IQ” is most literally where it came from. Together with “moron”, “imbecile”, “idiot”
Since we all agree that IQ is not an actual quantification of intelligence those words are now used as means to attempt to offend someone, without relation to their medical history or mental aptitude.