One of the purposes of college is to confront topics you're uncomfortable with or don't agree with and learn to 'agree to disagree' without acting like children.

I agree. Why couldn't the professor demonstrate that? Why try and force his (misguided, apparently) politics onto a group of students in a non-political class? Why conflate BLM with evolution, the black experience, or cultural anthropology (I'm assuming they weren't studying the culture around BLM, since there isn't really any)?

And removing yourself from a situation where you're literally unable to argue against someone grandstanding is about the most mature thing you can do. They didn't shout, or protest him, or try to get him fired, they just refused to put up with his bullshit.

I mean neither of us were there, so neither of us knows exactly what was said, but if an authority figure actually tried to defend BLM to me, I would lose a lot of respect for them, generally speaking. They're the largest racist organization since the KKK.