Seriously though, I disagree with the author. Don't acknowledge their words at all; going on the defensive and trying to prove that your are not what they claim is their point- they have won then. Simply ignore their accusations, and go on calmly with making your point and treat them as your intellectual inferiors, or as though you are talking to a small child.
I didn't care if my professors liked or agreed with my point of view, and I will not be intimated by the bleatings of fools.
I think the arguments suggested in the OP are OK, but too narrow in option. Most professors are capable of tying things up at the first question, definition of racism.
It is wise to be open to intellectually valid challenge, but when your opponent is an idiot, treat them like an idiot.
This is very much the more wiser course of action, though telling them to "f*** off" should be incorporated in there somewhere.