The bitter truth is, the community should never have let that situation develop in the first place.
And what gave the mob the grip it has on the US is our little governmental experiment with outlawing alcohol.

It's easy to ask that others sacrifice themselves.

It's easy to decide to kill people who aren't living up to your standards.

Yet there aren't ever many people willing to sacrifice themselves for their standards. (Strangely enough, this group includes the suicide bombers and cops and people like Ghandi.)

It is also necessary to appropriately define the "community". In the case of Los Angeles gangs, it might do to simply define "members" as the community, since there actually are powerful government entities to counter them.
Yet the gangs are powerful in their territories. And the gangs feed off of the larger "community". There's a balance of trade, first off.

But this gets back to root causes and such. The gangs provide a service, drug distribution. There's a conflict between the government and the gang and the gang seeks to preserve itself and its revenue streams.

I think we can learn a LOT from the parallels between gangs and terrorists.