Use the their own paranoia and love of mindless violence to turn them against each other. Like in Hammett's Red Harvest. Mix it up.

Of course, then we'll have another yahoo on our hands, just like the last one. But we can give him the same treatment. But if, by some miracle, we've all learned something from experience by now, we'll do it promptly, *before* this one demolishes an office building. As long as we don't repeat our historical mistake of assuming our puppet dictators are really our friends.

And just keep doing it until all the rival fanatical factions are used up. At which point, the Afghan people will perhaps be a bit the wiser.

Maybe it will work, maybe it won't. But it's worth a shot.