Take this extensive list of London riots dating back to the 12th century, for example:
http://en.wikipedia.org/wiki/London_riot
Some can be seen as clear expressions of social and political grievances, often peaceful gatherings triggered by police brutality; others, mindless eruptions over sporting matches or pogroms against against religious and ethnic minorities - the latter what you might call, to borrow from Bebel, the mass action of fools.