Tenure.
Once they have tenure, professors can be as stupid as they want to be and face few if any consequences.
There are in the real disciplines. You know, the ones where a degree in that discipline will actually get you a real job. Too many of the pseudo-sciences take on an attitude of victim-hood so that their ideas cannot be criticized without a counter-charge against the critic of being an oppressor.
Lots of interconnected parts to this problem but a big one is the academic world's obsession with diversity. It creates a group of people on campus who are marginally qualified (at best) but who have a degree of protection because the university needs its poster children and to keep its numbers in line with the quota needed. These diversity positions seem to really attract the activists. They get financial security, a platform, and protection from criticism for their foolishness.