Well plenty of liberal colleges have actual Republican clubs or Conservative clubs. It’s not just a couple of people like you say.

Sure, but I think we can agree they are a clear minority.

Anecdotally I experienced this as a liberal attending a military college. Sure there were other liberals there, but it was a 10-1 ratio. It was isolating - and just try to debate a topic when your prof has 30 years as a PhD and everyone else in the class backs him. At some point learned helplessness sets in. Would have been much better with a more diverse faculty (there were a couple of decent history profs).

Students can do this without right-wing teachers.

Correct. Most won't though, for the reasons detailed in the lecture. People prefer not to challenge the conventional wisdom - groupthink is a real phenomenon. University is a place it should be challenged.