I've heard this from various radical leftist college profs: if you give them a liberally slanted opinion, almost no matter how ill-justified, they will give you a pass. However, if you give them a well-supported conservatively slanted opinion, they will hand it back to you with a poor grade and questions up the wazoo, such as "what is the defininition of this?" (for some number of common terms) and so on, until you give up and change your opinion, or take the flunking grade.
In other words, the proper job of a radical leftist teacher is to harass any conservative students and modify their behavior to that of an incipient radical leftist. Only incipient radical leftists-- or those who behave like incipient radical leftists-- are permitted to graduate from these kinds of classes.
Of course, Skinnerian behavior modification is frowned upon as being obsolete in regards to any other educational context (eg, science and math "drill and kill"). And of course, the US as shown by TIMSS has fallen to 12th place or worse in math and science among the industrialized countries of the world when ed school research is actually put into practice in these subjects in today's US public schools. (But that's OK, since many US public school teachers and education researchers have science-phobia and math-phobia to begin with, and could not affect this particular side effect even if they wanted to...)
Teaching math and science is counterproductive for the left.
First, it teaches that there are absolutes, and measurements, and limits to measurements.
Second, teaching the scientific method teaches critical thinking tools; "if this is true, then this should be true, and I can check that by..." ("Bush tripled the National Debt" becomes a testable hypothesis rather than accepted fact).
Third, it calls into question Gloobal Worming, which is not to be questioned!