Hmm…so you had me until the end since up until then I agreed with almost every sentence. But I slightly disagree with your positive thesis for action. I know the situation you’re talking about (it was my discipline) and rather than the professor marching over to the office to give her a piece of his mind, he should have done something first. Namely, checked to see if the narrative he had was a) accurate and b) true.
If you know some of the nuances of the case, including the topic at hand that day in lecture and the policy the TA had explicated to her class about more or less encouraging a climate not of civility but where topics that *could* instantiate racist, sexist, or the like *conversations* may not be allowed during the class for the reason of climate, then parts of the narrative are dubious at best. It’s not that a few students disagreed, it’s that one posited it as an example of philosophical notion A (which it actually may not even be an example of and, if not, then it could also have been dismissed on those grounds).
Yes, if you’re sure that something problematic has happened then, when possible, reach out to have a conversation and see what can be done moving forward. But you have to make sure that the problematic thing actually happened in the first place.