How about you and everyone else just stop being so damn sensitive?
Sure it's a shame that people use Mental impairment as an insult degrading the hardships that those with said mental impairment go through no fault of their own are afflicted with.
But on the other hand it's a perfectly apt insult that fits the bill if your goal is to insult someone by association like say comparing a really stupid individual to a legitimately retarded one or a individual with poor eyesight to a legitimately blind one
Furthermore the knee-jerk sensitive reaction achieves nothing but changes the semantics like when retarded became "special" because the word retarded was considered insulting and degrading to those legitimately retarded yet "special" was later adapted as an insult as it has the same meaning.
All your pointless bitching is just that pointless bitching, because people are cruel, callous and clever.
Autistic seems to be the flavor of the month synonym which is ironic because while many autists lack cognitive ability in some areas like socializing they are often more technically gifted then there normal counterparts however comparing an unruly awkward anal individual to an autist is again an apt insult.