Well, again, there was once a time where that word wasn't some kind of a racial slur towards disabled people, and was more of a slang term for calling someone an idiot or a dimwit, and some people out there seem to still be stuck in that kind of immature/outdated mentality.
On that token, we can't even describe something listless and lackluster as "lame" anymore either, because apparently that's a slur now too. No wonder they say English in the hardest language to learn; we keep taking words out of context, make up new meaning for them, then take 'em out of that context and make up new meanings for them. I heartell that's why some countries try to abolish slang.