unless they are proud of being an idiot.

of their own idiocy.

Now, believing they're intelligent (Dunning-Kruger) and being proud of that despite the fact they're idiots...

and there is Stunning-Cuckoo. I've known a lot of people who were proud that they didn't get their edumacation in no fancy school. But, I think that the old saying refers mostly to people who refuse to acknowledge their idiocy is idiocy while being proud of it.

Sorely missed.