Socrates. The Socratic method is supposedly about teaching, but anyone who's read the Dialogues can tell you that what Socrates actually did was ask people seemingly innocent questions about their positions that forced them to contradict themselves and therefore look stupid.
The point isn't to make you look stupid. That's just something that usually happens.
The point is to cause you to question your underlying assumptions, and to take them to their natural conclusions, to find that they inevitably lead to contradictions. This forces you to reevaluate your underlying assumptions or at least realize that while they may still be generally valid, actual reality is more complex and requires exceptions or other accommodations.
The user of the Socratic method does not profess to have any special knowledge and may explicitly disclaim it, as Socrates did. However, the target of the method, at least among the Dialogues, written after Socrates by his worshippers to make him look good, usually does, and ends up worse for the treatment.
However, the challenge of the method teaches more than a lesson from on high. It teaches you to think critically, not just about the subject of the "lesson," but about the very method through which you reach your conclusions. This is why, as The Paper Chase portrayed it, it is often used to "teach you to think like a lawyer."
Most professors don't actually do this any more to the degree of a Kingsfield, perhaps because it's actually as difficult for the teacher as the student.
Also, perhaps, a lot of people these days are afraid of being mentally challenged, especially by someone who they aren't going to "win" against anyway. It's sort of like a dojo where sensei picks someone out of the class and kicks their ass every day.