Everybody is intelligent it’s just a case of what you reveal, the style you maintain that influences others one way or another. I don’t think anybody can be truly stupid.
For example someone’s good at diplomacy; they have a matured level of emotional affluence, so they make a point out of it and become adept at hiding what they’re not so good at.
Thus they get a badge for being intelligent, but they’re still bad at some things. Stupidity is trying to be good at everything with no regard for your human limitations. And,the chances are, in most cases stupidity is just a style that is maintained just as intelligence is. If you think somebody is stupid, scratch the surface and you will see that there’s something they’re good at, you just haven’t seen it yet.