I am so glad you posted this. Sometimes I get into little arguments about word usage and younger folk truly don't understand how not only commonplace word usage that is considered some sort of insult now but how officially they were used. Near me was a place that helped folks with all sorts of independent living including housing and job training and just counseling and it was called the NSAR and Im almost sure the R was retardation. Think it changed its name and I can't find anything on it now but I did find like this https://mn.gov/mnddc/parallels2/pdf/70s/70/70s-WWH-NARC.pdf
It's hard to fully explain how the reception of words change to people who haven't seen it first-hand.
Even some bad words, which might be incredibly rude to say today, didn't have the same oomph in the past, so while the definition technically might not have changed, the intended severity of it has.
yeah and part of it is they were used as insults but it was more co-opting than anything else. retarded is pretty legit as saying someone is retarded can be proper, but someone will call someone retarded who is not as an insult. then shortening is almost never correct. You might say someone is retarded and that is a correct thing about their condition but saying their a retard is not as its sorta a made up word based on the condition and further tard or tarded is a way to make it more derogatory. Its like homosexual. its a word that means something without being derogatory but to someone who thinks being a homosexual is bad will use it as an insult and using the word homo is almost always an insult (the rare exception is usage among friends to sorta deflate its meaning). When it comes down to it is that folks who spent decades with a word being legitamate will have trouble when it becomes a taboo thing for a decade or so.
I find it hard to believe lesser human would be used as a term. Its a bit funny because again midget was also used as opposed to dwarf by the relative proportionality even though dwarfism was appropriate for both types. Was it being used to describe someone in the show with dwarfism though because if not then it was sorta being used derogatorily.