To rabble-rouse, the character delivers a speech intended to transform the crowd into a mob, inciting violence against a given person or structure, in order that the individual be killed or the structure be destroyed. To achieve this, the character must make a strength check (strength of voice and apparent personal ability to carry forth the request is in doubt here).
It is presumed that the crowd is willing to become violent once the speaker sets out to encourage violence - however, if the strength check fails, the crowd will begin to argue amongst themselves. Within ten or twenty minutes, others will appear and the mob will swell from 2-5 times its previous size - whereupon they will begin to fight among themselves. Soon a full-throated riot will result, so that every building within a one mile radius has a 1 in 20 chance of being torched or destroyed through looting. Since the crowd will have divided into factions, the first will set out to perform the character's original wish - destroying every public building within reach - while the latter faction will take it upon themselves to attack the character or the character's possessions. Presume that the number in each faction is equal to the original size of the crowd before the character began to speak, +/- 10%. The riot will last for 5-15 hours before finally dispersing.
If the strength check succeeds, the crowd will organize as a vigilante force itself as directed by the character and set out as best they can to perform the actions desired. If it is possible to destroy buildings they will, if they are able to find the villains, they will do so. However, the crowd's anger will diminish once 2-12 hours have passed, whereupon they will begin to disperse.