To me, it seems actively harmful to accurate thinking, happiness, and your chance of doing good in the world.

Interesting. The terms 'mundane' and 'smart' always pointed out to me that I am part of a group that is perceived as 'other' by some people. I have to be more Machiavellian at times when dealing with mundane people ('opposed to smart' more than 'not smart'), but I don't consider most people mundane. That said, I have no idea if this interpretation is how other people see it, or if it's not the intended interpretation.