Well, bear in mind that intelligence and insanity often accompany one another, and I doubt university job interviews focus as much on the second as the first. So it may be that the occasional crazy Phd could sneak through the system, and start grading your papers. Read about just such a case here, regarding UT Arlington professor of philosophy and law, Keith Burgess-Jackson. I hope it serves as a sign to other students that, when your prof is driving you crazy, it may be because he already is.
*Note: be sure to follow the links within Leiter’s post. They’re even more elucidating.