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.
The N word is based off negro which is just black. Calling someone black isn’t an insult so the only connotation would be to be racist. Retard is based on slow and I would want to call someone slow and imply what they’re saying is moronic, so it literally fits perfectly. That said it’s still used as a slur pretty often and it’s purely a negative word so I still don’t really use it.