By 1773, the Americans had been pushing back against Parliament's efforts to tax the colonies for roughly a decade. In 1764, Parliament passed the Sugar Act, and in 1765 the Stamp Act. These laws sparked intense resistance. The Stamp Act, requiring that all papers – legal documents, newspapers, and other publications (in addition to playing cards and dice) – bear the King's stamp as proof of having paid the tax, sparked intense resistance, often in the form of mobs which gathered to ensure that no colonist was foolhardy enough to be the official stamp agent. 

According to an old nugget of wisdom, the key to a good tax is to pluck the maximum number of feathers from the goose with a minimum amount of squawking. From that perspective, taxing writers, publishers, and lawyers was particularly ill-conceived. 

But how to protest an act that faraway British subjects, with no representatives in Parliament, regarded as illegal? The colonists believed they had the right to tax themselves in their legislatures which were, significantly, the only elected legislatures in the Americas at the time.

In an age before elected legislatures were generally understood to be the heart of the government, mobbing was sometimes recognized across the board as a legitimate, albeit extreme, way of vetoing what the common people regarded as an unconstitutional law, or of blocking an illegal action by the government. Hence, colonists would distinguish between legal and illegal mobs.

Such mobs generally reflected the opinion of the local majority – they were not part of street fights between factions. Some of the Stamp Act mobs did get out of hand; others were more restrained (perhaps not by the standards of our more civilized age) and the colonists succeeded in blocking the Stamp Act, which was repealed.