Commentary has just published an excellent symposium addressing the question: Is free speech under threat in the United States? Top-notch contributors include Richard Epstein, Heather Mac Donald, John McWhorter, Harvey Silverglate and our own Eugene Kontorovich.
In my own contribution, I lament the increasing intolerance for any views that challenge liberal orthodoxy on campus, and I offer a partial explanation: “The free-speech crisis on campus is caused, at least in part, by a more insidious campus pathology: the almost complete lack of intellectual diversity on elite university faculties. … If students are shocked at the prospect of a Republican behind a university podium, perhaps it is because many of them have never before laid eyes on one. … This may help explain why some students will do everything in their power to keep conservative speakers off campus: They notice that faculty hiring committees seem to do exactly the same thing.”
The Commentary symposium is available here.