Let me have men about me that are fat,

Sleek-headed men and such as sleep a-nights.

Yond Cassius has a lean and hungry look,

He thinks too much; such men are dangerous.

You all remember Cassandra, right? Basically, she was smarter than her neighbors, but they didn't believe her. Why?

Imagine where we would be if we believed what intelligent people said, given that we can't really tell who is and who isn't intelligent. The sky would always be falling. That's the heart of it. To defer to intelligence is to empower it, and power tends to corrupt. Better to shun the geniuses and wait for events to prove them right.