I was thinking about it a few minutes ago while eating a packet of ramen.
Sure, you could think about it from a simplistic point of view like "gangz r bad, they kill peeple!", but then again look at all the religious based wars and "crusades" in history.
They both follow a code of conduct of some type.
They both are always actively recruiting new members.
They both have specific things to wear and not to wear.
They both like making people uncomfortable.
But, I think I'm relating this more to tribalism or something, considering you could compare similarities between any groups of people.