[zahlman]

>I’m referring to the deliberate and inherent mean-spiritedness towards people with intellectual disabilities that the slur is explicitly invoking.

I disagree that any such thing is invoked. It seems that you believe that when the word "retard" is used in these contexts, that it's meant to describe a person with an intellectual disability. I think it's merely intended to describe someone of low intelligence, which neither necessarily qualifies as nor is necessarily caused by a disability.

Nor do I agree that it's mean-spirited in a way that, say, the word "stupid" isn't. It's just more intense.