A few years ago, one of my kids sent me a frenzied text saying a protestor was harassing kids at her school. Several things went through my head, not all of which I can print in a family newspaper.

Siddhu Pachipala is a student at MIT. On the last day of a seminar I took at Harvard called The Success and Failure of Protest Movements, the professor circled the room with a final question: Should ...