The R Word & One of My Soap Boxes

I just watched a video about a dad's story of his daughter with Down Syndrome and have tears streaming down my face. A little background on this story...

A word that I really dislike and that people use casually is Retarded.

I've heard people who are over-the-top PC use it.
People who
never would speak derogatorily about another race
abhor anti-homophobic putdowns
despise the use a negative phrase to make light of a mental illness
don't utter a curse word
describe themselves as open-minded
believe that everyone should be treated equally.