Ehhh it did used to happen. And it didn’t have to be someone with debilitating issues as strong as down syndrome or autism. Back in the 90’s everyone from dyslexics to down syndrome, to people with social anxiety were called retarded. Even a simple idea got called retarded if it wasn’t the norm.

That being said, people who throw people in concentration camps shouldn’t be called retarded. They should be curb-stomped.