It's baffling anybody would think otherwise. Reddit auto-censorship (and such auto censorship elsewhere) has a lot to answer for.
See the other comment where the guy mentions it's overwhelmingly used in a non-cursing manner, then the first hit is it being used as cursing.
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'.