Student thuggery against non-leftist viewpoints is in the news again. Agitators at Claremont McKenna College, Middlebury College, and the University of California’s Berkeley and Los Angeles campuses have used threats, brute force and sometimes criminal violence over the past two months in efforts to prevent Milo Yiannopoulos, Charles Murray, Ann Coulter and me from speaking. As commencement season approaches, expect “traumatized” students to try to disinvite any remotely conservative speaker, an effort already under way at Notre Dame with regard to Vice President Mike Pence.

This...