You make the mistake of substituting knee-jerk emotion for reason and logic. First; there is no evidence provided by the author that any of this actually happened. Second; even by her own account, the professor did not say or do anything remotely racist. This article is after all an accusation of racism against the professor, but not one single example is given of anything racist that the professor did is supplied and once again; no evidence.
Third: The author clearly takes a disagreement on a point of history and turns it into a race issue based on nothing but the colour of the professor’s skin. She brings up race over and over again and she clearly measures the validity of what everybody says and does by their race. She does this all through the article.
If what the author is saying about the professor is true (which I doubt because no evidence is provided) then the professor behaved abysmally just as the student did too. But unprofessional behaviour does not constitute racism; nor does disagreeing with a black student over a point of history; a point which that student had obviously not researched.
Finally your rat invested building analogy missed the point entirely. Anyone can jump up and scream “rats” just as anyone can scream “racism;” but if you want someone to believe that there are rats; then you need to show them some rats. The student completely failed to produce any rats, and no; the student does not have any experience of living in a rat invested building. The student was arguing about a rat infestation that was long over before she was born. The discussion was about slavery. The student was never a slave, and her skin colour does not qualify her to understand slavery any more than my skin colour automatically gives me some profound understanding of the holocaust. Historical knowledge has nothing at all to do with skin colour.
And no: Nobody should be shackled. I have no idea where you are trying to go with that. I am simply saying that by the authors account, she took a disagreement over a point of history and turned it into a completely unfounded accusation of racism against the professor.
Better luck with your virtue-signalling next time.