I’m guessing using the term liberal is the incorrect term.
Classical liberalism is a whole different thing. The professor is making the correct distinction.
Old school, genuine “liberals” really are “tolerant”—of different people and ideas, while exercising discernment, in order to distinguish between truth and falsehood, right and wrong.
He is pointing out that the cultural Marxists have twisted and distorted everything. They themselves are tyrannical, totalitarianists-—not tolerant or even inquisitive, thus not really liberal at all.