We shouldn’t call them retarded. We should refer to them as the accelerated.
The ironic thing is that any new term the PC police come up with will eventually morph into a new pejorative for someone who acts dumb but isn’t actually retarded.
People (especially women) who had mood swings used to be referred to as “manic depressive” back in the 80’s (especially by their boyfriends), then the psychiatric community changed the term, and now those same boyfriends are “bi-polar.”