It's not just the intellectually challenged who make mistakes
At university, we had PhD students helping out the professors teaching us.
One of the PhD students
proved something that was plainly wrong, and we lowly, fresh students proved him wrong.
This happened not just once, but 4 or 5 times while he tried to prove his theory in a different way, and every time we've proven him wrong.
He grabbed his stuff, and walked out of class after maybe 15 minutes.
We didn't see him again that day