Its not about bias. Professors honestly believe that what they are teaching you is the truth and that their viewpoint is the correct one. They don't want to hear your ability to argue with them or present critical thought. They want to know that you absorbed their viewpoint. When you write a paper contrary to their viewpoint, they see it as you not understanding the material, not as you understanding the material and choosing an opposing viewpoint.
I think you and I have described the same thing using different words. Just because someone doesn't know they have a bias doesn't mean that they don't have a bias.
There's a bunch of replies all over this thread that are almost comical examples of HN users trying to rebut the positions of people they agree with.
I don't know if that's because internet commenters in general just use the preceding comment as a springboard to jump onto their own soapbox, or if HN users are particularly bad at reading and responding to the content of a text (while loudly denouncing such worthless literary skills).
