This is just another case of right-wingers using their general "thesis" of liberal bias as the overriding factor over proof or facts. They focus on a set outcome and then search for anything that backs it up, while ignoring anything that disputes it. They believe things because they want to believe them. And it doesn't occur to them that the process should work in reverse: getting the facts first and then arriving at the thesis based upon those facts. And any additional facts should be included into the thesis, rather than ignored.
But for them, any evidence to the contrary is considered to be just a fluke or in dispute or biased. If something confirms their beliefs, they immediately jump on it as proof of their thesis, and will shout to the high heavens that it proves their thesis. And any fact which needs to be assumed (liberal professor) to make the thesis work will be promptly assumed until firmly proven otherwise. But even then they instantly become the champions of "let's wait for ALL the facts" when those facts go against them. And then they promptly forget about the story, in search of more facts which back up their arguments. For them, facts are merely examples used to prove their arguments, rather than the basis of those arguments. And that's why it's perfectly ok to ignore "bad" facts, because they already believe their argument to be true and are simply looking for their proof. Something is true because they believe it to be true intuitively.
As for my opinion on Professor bias, it's all crap. The point of education is not to receive a confirmation of your point of view. The point is to learn different points of view. And if you don't know the material well enough to answer a professor's question the way that they want to hear the answer, then you're a schmuck who deserves the grade you receive. I've had many teachers who pushed points of view that I disagreed with, but I was able to get A's (I graduated Summa cum Laude). And I've also protested grades which, in hindsight, were well warranted; while I was acting like a jackass.
In this case, I firmly believe that if you can't explain someone else's point of view in a way that they agree with, then you are unable to disagree with them because you don't even know what they think. You can't honestly disagree with what you don't understand. And if you disagree with a professor, you can explain why you disagree...but only AFTER you've successfully explained their point of view and what it is that you're disagreeing with. Anything else is intellectual dishonesty. Had this student first successfully explained how Cohen's deviance theory (whatever that is) applies to the example given in the question, then there would be nothing wrong with explaining why it is incorrect. But instead, she chose to give an unrelated response and, having failed to fulfill the requirements of the question, received a poor grade. And that is exactly how education should work, regardless of the professor's personal biases.
Any intelligent person should be able to explain a point of view without needing to subscribe to it. I can fully explain supply-side economics, yet I think it's a fairly useless theory these days. And, yes, my supply-side-biased Republican economics teacher gave me an A, even though I completely disagreed with what he taught.
Again, college is not about confirming your POV; it's about understanding other POV's. And if you believe that too many professors are pimping different POV's from your own, then you're just getting a better college experience than everyone else. But that doesn't give you an excuse to hide within your own POV and expect the professor to respect it. That's just being a jackass.