I have used the term retarded, which before it was used as a mental description, simply meant slowed down or held back. My goodness, the older cars.. such as models A and T, had to have their spark 'retarded' along with reducing the throttle.
I have used the term "retard" as a descriptor of a person perhaps a few times, but not on a routine basis, knowing it carries a negative connotation. Actually I have never used the term to describe a truly challenged individual, but to describe a politician or leader who makes what seems to be an incredibly stupid move.
Language usage is an interesting phenomenon, because the meanings of the words change during popular use.
For instance, years ago some people thought the term "queer" was a word that conveyed hostility..so the opted for "homosexual", thinking that was less so. ..But soon in the public mind, homosexual took on a sense of disgust.
So, the advocates co-opting a common term..calling the same habits, "gay". Today, that term is often used as
a negative comment.
You can change the spelling all you want, but you cannot change the common perceptions so easily.
Sadly, years ago people who were mentally challenged, may have been called such adjectives as dummy,
moron or stupid. Thinking to ease the situation, some folks suggested that such unfortunates be referred to
as being "retarded"..then a more kindly term.
Soon however, it was truncated to "retard"..now a pejorative term.
Again....You can change the words, but you cannot change the perceptions.