Residents of Christiania in Denmark may vote to end open cannabis trade over fears of rising gang violence

I think that gangs are not products of capitalism since they have existed in nearly every form of society. Rather, gangs exist where there is incomplete state monopoly on violence.

Gangs are essentially proto-states.

They implement varying political structures, ranging from anarchic to democratic (like pirates) to feudal to autocratic (like some cartels). They organize for their members' economic and social interests where the state fails or refuses to serve those interests. If there's a strong enough interest in drugs, someone or some group is going to serve that interest if the state won't.

Like states, gangs seek to consolidate power and violence. When there are multiple gangs and an unstable balance of power, you end up with a deadly Warring Kingdoms situation. Paradoxically, a place become quite safe when a gang establishes a complete monopoly on violence and becomes a functional state, like some favelas, complete with gang-run social services as well as gang police, military, and legal and judicial functions. Gangs eventually end up with their own accountants and IT services!

Also paradoxical is how incomplete disruption of gangs by state police can stoke even more gang violence, like in Chicago: it can disrupt a relatively stable power balance by dethroning established gangs and gang leaders, leaving power voids to be re-contested by both old and new gangs.

El Salvador attempted complete disruption of gangs by basically incarcerating everyone who was remotely involved in a gang and then subsequently filling the massive power void with state power. They managed to reduce its murder rate by an incredible 90%+ percent in under a decade.