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.
it’s historical and cultural context.
hence why words that were once common place, become seen as heinous.
but it’s not like words are the only thing for which this is true. just look at say, attitudes towards sex.
and the moralists about sex/words will argue that everyone else should do/believe what they do, or they are bad people.