Well, when my dad, my sister, their friends, and I are joking around, we use the word retarded. For the longest time I didn't know the true meaning of of retard, so I thought it was okay. I only use it sometimes, but normally I use the word "derp" in place of it. I am sure some people would get offended by the misuse of that word, and people have. Really, you made a good point, it's not okay to use it that way, and people should really stop, but we can't control them, so this is a reminder.