On the topic of bad teachers, two friends of mine had a psychology professor who refused to admit that the units of "nanometers" existed. The correct SI units were, of course, millimicrons. Believe it or not, his contract was not renewed for the next year.
Also, a friend in a Chem 101 class had this grad student who told the class that "0 degrees Celsius was absolute zero," and that "paint was a solution as long as you kept mixing it." Yeah, that's right, a chemistry graduate student.