This is a slightly touchy subject: Professorial control over in-class language. But I'm going to broach it anyway, and in perhaps an unexpected area.
A bit of language reported to me as having been used by a student in a college class lately (not one of Esteemed Husband's classes, in case anyone is wondering), during a discussion of personal identity: "Well, suppose you were in an accident, and after that you were just a carrot..."
I'm guessing that most professors would not allow students to use the n-word in class. Just guessing. I want to recommend that, in that same spirit, professors (and GA's, etc.--all teachers) put the same ban on referring to a fellow human being in the utterly degrading way that that student did.
Given the topic of class discussion, and given the current status in our society of the student's views, I suppose the teacher had to treat it as in some sense acceptable for the student to opine that a person in a long-term comatose state is a lesser human being. Frankly, I'm quite open to the position that in a better society it would be unacceptable in polite company to speak of any living human being as life unworthy of life. Another bit of student talk reported to me from a college class lately, approving of the proposal that a physically healthy "bum" be killed for his organs: "Well, he's not doing any good to anyone now, so at least then..." Presumably if a student showed up in class and said, "It would be okay to cannibalize a black person for his organs as long as he was going to be used for a superior race. That would be doing more good to society," his view would be treated with open horror and disgust by everyone else in the class, including the teacher. But teachers, even those who are horrified, apparently feel that they have to be "professional" when it is only "bums" or the severely cognitively disabled whom their students speak of as sub-human.
Well, okay. I guess.
But at a minimum, if a student is going to express the hateful view that some humans are sub-human, he should have to do so in precise and non-disgusting language. No "carrot" talk. For that matter, no referring to another human being as "a vegetable." It is most unfortunate that the adjectival form, "vegetative," has entered our medico-legal lexicon and is actually used in law. But even there we see a very slight shying away from the outright contempt of the noun form. The noun form should be out of bounds. As Wesley J. Smith says in comments at his blog, "We don't use the v-word around here."
If you teach a class where these subjects come up, I encourage you to adopt these standards. If a student speaks of another human being--hypothetical or real--as "just a carrot," simply look at him and say this: "Justin, this is an interesting discussion, and you are free in this class to express your opinion that some living human beings should be thought of as sub-human. I disagree strongly, and we can have a discussion about it. But you may not in this class refer to a living fellow human being as 'a carrot', anymore than you may in this class refer to a fellow human being as 'a nigger'. I hope that is understood. Now, try restating your position in other terms."
Heavy-handed? Too bad. If any language is unacceptable in class, this should be.