[themacguffinman]

I think it's because mental ability and personal worth is pretty strongly tied in the modern world, in that way calling someone deficient is like insulting them. I don't know if you can escape that dynamic, intellect is just very important in modern work and culture. To judge someone as mentally deficient is essentially relegating them to the bottom rungs of the modern economy and status hierarchy in a way that judging athletic ability doesn't do, so naturally it's not comfortable for people to make that judgement.