Inflammatory public speech rises steadily before outbreaks of mass violence, suggesting that it is a precursor or even a prerequisite for violence, which makes sense: groups of killers do not form spontaneously. In many cases, a few influential speakers gradually incite a group to violence. Violence may be prevented, then, by interfering with this process in any of several ways: inhibiting the speech, limiting its dissemination, undermining the credibility of the speaker, or 'inoculating' the audience against the speech so that it is less influential or dangerous.Such efforts must not infringe upon freedom of speech, however, since that is a fundamental right and since free speech itself may help to prevent violence. Before acting to limit 'dangerous speech' - speech that catalyzes violence - we must have a means to distinguish it from other speech, even that which is controversial or repugnant.
Prof. Susan Benesch has developed a set of guidelinesfor making the distinction as part of the Dangerous Speech Project. The guidelines are based on the insight that the dangerousness of a particular speech act, in the context in which it is made or disseminated, depends on five variables: the speaker, the audience, the speech itself, the historical and social context, and the means of dissemination. For example, some speakers are more influential than others, and some audiences are especially vulnerable.