The site I quoted, altho it has a community forum, provides and uses evidence-based research. I don't say it's infallible, but it's not rubbish either. Understanding the issue of gang culture is unlikely to come from main-stream media or the "red tops".
We probably don't have the scale of deprevation that parts of the UK have, but we do have a sub-culture. Walk down nearly any main street and you'll find gangs of lads etc. I'm not saying they're violent gangs, but we do seem to have a macho culture of drinking and drugging, that could lead to it.