Sorry for the delay - getting my thoughts in order on this.
You play on their cultural fears, not ours.
First off, understand that death holds no terrors for the scum. They want to die. They are, in the main, completely indifferent if their family suffers for their actions after their death. So hitting the families is out. All it does is piss others off when they see it, and elevate the respect given to the "martyr."
In the event of a successful attack by the scum, give a total blackout of the names. Desecrate the bodies, publicly. Doesn't have to be anything dramatic, just throw them into the street, under armed guard, for the dogs and birds to pick at.
Any you take alive - they disappear. No mention ever made of them. No trials. No detention. They are simply gone. Then, after a few weeks have passed, release one fairly close to his home, completely unharmed and well fed. The rest - well it's a big ocean and stones are cheap.
If you are not in a position to take them alive - say a squad on patrol runs into a bunch of scum - kill all bar one. Maim that one by removing both hands and their tongue, then release him.
Brutal, yes. It also works.
