Try telling that to my boss, who has an autistic child. I held your opinion until I stuffed my foot in my mouth in a meeting. Now I don't use that word.

Wait until a derogatory word being used effects you directly. It's really easy to just not use words flippantly that you know some people have an issue with. You are clearly aware of how it can be offensive and for a lot of people your definition is still just a callback to people being unkind about mental illness. History matters too and if you choose to ignore that and use it anyway you're just being unnecessarily inconsiderate.

That may be so, but its active usage in one social group does not justify the discourtesy of its usage, especially in a professional setting.

Yeah, people are idiots. Incremental progress is better than nothing, though.