A commentator on Biased Teaching, Part III said he thought that a labeling scheme for courses with an ideological slant would be impracticable. I disagree. In fact, this is probably the simplest mechanism one could possibly design in this area, since it's based completely upon self-identification. Professors who want to teach a class that is designed as a forum to present their own views would simply identify it as such, possibly with a special code (so courses like this would be 205-B, with the B as the identifier). Students would know what they were getting, and they wouldn't have to take a class such as this if they didn't want to. On the other hand, classes without such an identifier would carry an expectation of even-handedness in the selection of reading, and at least a serious effort by the professor to present a reasonable selection of alternative views, even if the professor severely criticized them in class.
Once again, I don't think there should be a formal sanction involved here, although university's should certainly be able to take fidelity to the identification system into account in rating professors' teaching for the purposes of tenure, promotion and salary review. I also think that if ALL the classes that were identified as presenting the professor's views nearly exclusively were obviously on the left, that would visibly suggest a problem that someone should consider remedying. But again, I think the solution here involves information and visibility, not some bureaucratic system for collecting information and creating a quasi-affirmative action system on the basis of ideology. This is a problem that is subject, at least at the margins, to a libertarian remedy.