I don't think Trump supporters are stupid. And I cringed when Cruz hinted that a while back. I just wish more of them could be critical of him from time to time and have a little more skepticism.
I think that's fair. However, a willful failure to approach one's beliefs critically is not a sign of intellectualism, or curiosity. It's not "stupid", but the present circumstances it is something much darker.
It's a bit like rooting for a sports team. Loyalty to the team, and defensiveness toward others fans' criticism, keeps one from recognizing those flaws which could lead to disaster. "Fan" of course, is derived from "fanatic", and Trumpsters tend to exhibit traits of fanaticism. And both the worlds of sports and politics have occasionally been marred by mob violence.