The question pretty much covers it. I love learning about various subcultures, and the way citizens of a larger society set themselves apart and express themselves. Any examples from history?
In 6th century Constantinople, chariot racing fans formed what essentially amounted to two rival gangs, the Blues and the Greens (the similarities to the Old Firm is most likely coincidence). It has been put forward, though not universally accepted, that these groups tended to be split on issues of religion as well as sport. However, their post-race riots over the years resulted in thousands of deaths.
In 532, the Blues and the Greens combined to stage what amounted to a revolt against the Emperor Justinian, which was ultimately put down resulting in tens of thousands of deaths and the general end of that racing culture in Byzantium.
Source: Blue versus Green: Rocking the Byzantine Empire, the Smithsonian
PS. If anyone has more information on the Blues and Greens, particularly more details about what being in one of these groups was like, I'd be really interested to hear it.