Is a writing classroom big enough to hold everyone's ideology?

Let's just get this out the way, shall we?
Pulling My Hair(ston) Out
Hair(ston) Today, Wrong Tomorrow
I'm Gonna Wash that Leftist Right Outta My Hairston
Come On, Maxine

I think Mark's right that teachers have less power than Hairston attributes to them. But I do think it's wrong for a teacher to stand up in front of a class, state her political views, and then assume that that somehow opens a dialogue. In true Berlinian fashion, I will quote two student texts to make this point (as opposed to quoting, say, Moby-Dick – boo literary canon! Viva la resistance!)

I ask my student to write a short reflective letter to me after they've read my comments on their first submission of their paper. Here are two excerpts (which I am consciously co-opting for my rhetorical purposes):
I really don't see the big deal about using cliches, but if getting a decent grade requires not using cliches then I won't use them.
I agree with all of your comments, on the basis that I am a student learning and you are a student trying to obtain your masters so I will take your opinion. Also you are the one grading my paper so I will do it how you want me to to do it.

Besides the obvious contempt here, we can see the students acknowledging and submitting to my power over them, despite their personal disagreement. “I believe something,” they seem to be saying, “but you say it's wrong, so I can't say it's right.” What irks me is that now it's irrelevant whether or not I tell them why cliched writing is bad, because any knowledge I impart is received as “stuff I have to do to get an A” and not “stuff this smart person thinks for good reasons.” Teachers who mean to foster openness by being open about what they believe miss the point that students, particularly at the freshman level, are less concerned with the ability to voice their opinion than they are with grades. We don't conceal information to be deceitful, we conceal information so that the students' views aren't trumped, shoved aside, or replaced by ours.