We are all "smart" in some ways, less so in other ways. Trump is smart in some ways, enough to get himself elected the President. History will be kind to him.
Calling someone "idiot" says more about the speaker than the target of the epithet. It shows hatred.
The feeling of hatred, especially toward someone not personally known, is often a distraction, away from the real problems that are troubling the afflicted, who lacked the courage to face the real problems in life. That distraction offers relief.
So, what is actually troubling your child?