Gangs tend to have their own culture, which is usually influenced by the identity of the core members, their goals and aspirations, but most importantly, their beliefs.
Red Rage was, as the name suggests, a gathering of very angry people. The reasons varied, but each of the member acted as if their blood was on fire, ready to erupt at any moment. The violence they commit rarely has any goal or logic behind it, which has earned them the reputation of a bunch of savages with no restraints.
Of course, if that were all there if to them, they would have been wiped out long ago. The gang has existed for almost a decade now, and they wouldn't have lasted that long if all they did was go around beating people.