I don't think it's auto-censorship as much as language changing. For me, 'retard' is 99% associated with my friends dissing each other as kids, and 1% associated with 'delay'.
Meh. Probably more likely is those damn automod settings on reddit (which aren't, you know, configured by moderators according to what their community wants or anything)
Autistic is also being used this way but its long-term fate is not so clear to me.
In general euphemisms cannot keep up with bigotry, I rather consider it a lost cause.
I don't. It doesn't seem to be that difficult to be aware of these things, and if I can save others from feeling the twinge of pain from being reminded of their childhood, or other abusive memories, simply by not using a few words... why wouldn't I?