Victor Xie,
"Stupid" is not a quality that you possess, it is something that you do. Don't judge people by outward appearances or reputation, judge them by what they do.
There are a number of expressions using the ___is as ___does formula.
Stupid is as stupid does.
Beauty is as beauty does.
Evil is as evil does.
Each is a variation of the same basic meaning.
You can even invent your own!
Handsome is as handsome does.
A hero is as a hero does.
Italki is as Italki does.