Thoughts on the Word Retarded

I was recently at a sleepover with a bunch of friends, and we decided to visit one of my friend's brothers, who lives in a group home. We went, and it was a really nice experience that was much less scary than I anticipated it would be. As we left, I wondered what would have happened if someone had said, "Oh, that's so retarded" or something to that effect while we were around several mentally challenged individuals and advocates for them. Clearly lightning would not have struck them down, but I'm sure there would have been an awkward silence or even a gasp or two, several scandalized people, and a lot of apologies from the person who said the offensive word. I know that I was watching my mouth even more than I usually do to make sure that I didn't say anything that I would regret later on. I realized that I should be just as watchful even when I'm not around mentally challenged people. The word retarded is really just a horrible word that shouldn't ever be used, and I know that I'm going to do my best to stop saying it in the future.