Stop dreaming. The real world is here, now.
There's a reason Ender's Game is on the reading lists at a couple of the military academies. The Ender defense is basically this: when you are being threatened, take your enemy out in such a way that the enemy can never again be a threat. In the book, he killed two other children who attacked him. It's a personal application of the old Machiavellian principle,
Upon this, one has to remark that men ought either to be well treated or crushed, because they can avenge themselves of lighter injuries, of more serious ones they cannot; therefore the injury that is to be done to a man ought to be of such a kind that one does not stand in fear of revenge.These feral gangs are becoming such a problem that I would say such a solution is viable. Only fear of death will stop them, only death will keep them from coming after the victims in reprisal for snitching or attempting to defend themselves.