When does political anger turn to violence? Rarely

Furthermore, the psychological distance between talk and action — between fantasizing about even so much as brick heaving and actually doing it — is far larger for a typical, peaceable citizen than many assume. In the aftermath of the July 2007 London subway bombings, for instance, polls found that about 5 percent of Muslims living in England said that they believed violence was justified in defense of Islam. “That projects to about 50,000 Muslims in the U.K.,” Dr. McCauley said, “but very, very few of them are acting violently.”

Kathleen Blee, a sociologist at the University of Pittsburgh, said the same was true even for groups that consider violence a central tenet. “In the white power groups I study, people can have all kind of crazy racist ideas, spend their evenings reading Hitler online, all of it,” she said, “but many of them never do anything at all about it.”