People (of all races) tended to be insensitive to the mentally ill. Institutionalized patients were lucky to be called “unfortunates” or something similar, but were just as frequently referred to as “defectives.”
Moron, imbecile, idiot, and other words that today we cringe to hear, were used frequently and had clinical meanings that denoted particular degrees of intelligence. However, to call someone a moron, for instance, instantly belittled the person, whether it was meant clinically or descriptively.
Americans frequently found humor in mental deficiency, and in the 1940s a comic book called “Little Moron,” written by Abbott Hoecker and Clydene Oliver (Heck and Ilda) surfaced. “Little moron” jokes were popular for years, though they don’t seem to be as acceptable nowadays.