Active violence is the violence of people who break windows or skulls.
Passive violence is the violence of those who would yield to nothing but active violence. It was Johnson's passive violence which provoked their active violence. President Nixon went even further, declaring well in advance that the marchers would not make the slightest difference to him. Violence on university campuses is of special significance. The way to prevent it is to avoid passive violence, which means that our authorities must listen to the protests of those they supervise with sympathy and human understanding.