Why did riots in response to the 2005 Danish cartoons depicting the Prophet Muhammad occur in nine Muslim states but not in 43 other states in which Muslims form a majority of the population? I show that the location of the cartoon riots is best explained by combining insights from the study of politics with arguments from the sociology of religion. Protests were mobilized by radical Islamist movements alarmed by the moral threat posed by the blasphemous cartoons. In states characterized by political rights and civil liberties, regimes responded haphazardly to the demonstrations, leading to confrontations between security forces and angry rioters. This finding can be generalized beyond the Muslim world: We should expect reactive religious violence wherever fundamentalist movements are confronted by transgressive acts, committed by threatening opponents, in a political environment that permits protest but fails to protect the religious principles of the movement.