There is always the Internet.
Usually it would be some common mistake/misconception, eg. applying special relativity in a non-intertial reference frame, but occasionally it might give a real insight into the analogies and methods used to teach a concept.
Say that you encounter a conspiracy theorist. When you point out that his theory is crazy, you don't want him to propose to agree to disagree, right? At that point, I feel like I might be wrong, because I'm the most argumentative. Get what I mean?