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.
Once upon a time it was the other word (it is a technical word meaning: delayed). Scientists and Doctors used it as the official term for mental development disorders, which is why people started using it as an insult.
Pick a different word and watch the same thing happen again.