The Book of Proverbs in the Bible has it right...Do not answer a fool according to his folly, or you yourself will be just like him. Proverbs 26:4 The meaning is that we should not lower ourselves to the fool's level by answering his silly questions or arguing with him as if he were a sensible man.
Darius Foutoux has an interesting observation on his blog. Another blogger summed it up...”We have no scale for stupid people. No measuring stick for stupidity. For smart people, sure. “She’s a genius. He’s a real Einstein. But what’s the measuring stick for stupid people? I mean who in history really stands out as the pinnacle of stupidity? It can’t be someone who’s merely narrow-minded, tunnel-visioned, and devoid of imagination”…READ MORE.
13 signs your coworkers think you're dumb – an Business Insider article
Five Basic Laws of Human Stupidity