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.
I find it difficult to imagine a future in which humans aren’t making fun of impaired cognition.
I think the context is what’s most important, if anyone actually directs such language (be it retarded, idiot, etc) towards people with genuine mental impairment, that constitutes a slur. But the word ‘retarded’ literally means ‘slow’, and is still regularly used (including by myself) in scientific and technical contexts (compared to racist or homophobic slurs, which are only ever really used in a ‘slur’ kind of way).
I wouldn’t really have a problem with calling people ‘slow’ in jest, and I don’t think many would. Imo if not ‘retarded’, it’ll be something else with the same meaning.
Also commonly used in timing of internal combustion engines