Ralph Peters explains it all: "We need to kill them first."
I think his wider point is correct. I also think he's still indulging in the armchair quarterbacking when he castigates the administration as much as he does for not being more aggressive: Part of the point was to have Iraqis (and moreso, an Iraqi government on all appropriate levels) be the ones to say "Please, come into our holy places and slaughter the insurgents", else we'd be fighting a lot more insurgents, along the lines of the entire population of Iraq... in my opinion, anyway.
