They switched up the policy this year and 'invited' white students and professors to stay home from school and work. The biology teacher wrote an email explaining why he would be attending work that day. Then they marched on his classroom, demanded his resignation and later demanded the university terminate him.

It didn't happen in a vacuum though. There was already friction between the protesters and Weinstein leading up to this (which I pointed out as being a pretty good sign that Weinstein has his own possible integrity flaws). He's an evolutionary biology prof. And evolutionary biology is racist and a tool used to maintain white supremacy.