Indeed, empirical and practical, not areas where there is much evident expertise on this list. CC was in the military, I seem to remember. The closest I ever got was Sgt. Pepper's LHCB.
If we are being empirical and practical, let's spin it from the no military response position. What is the practical implication of that? As KW says, it's an incentive to more attacks from a wider circle of nut-jobs. More specifically, the notion of no response begs the question of the attackers' motives. If we grant them some degree of rationality, we need to consider that their desire is in fact for the U.S. to invade Afghanistan. Why else pull the tiger's tale? Why expect anything else by doing so? No response just tells them they need to do more, to kill more Americans. Why might they want the U.S. to invade? For the same reason Zbig says he wanted the Soviets to invade.
The efficacy of U.S. military action is certainly to be doubted, but that is not really the main line of the left. Carrol departs in a curious way by focusing on the premise that U.S. response will not work, not that it is immoral or a political blow for reaction, U.S. hegemony, etc. In fact, if CC is right, the U.S. power and hegemony will suffer from this, not the converse, and this knowledge is unique to CC and unavailable to the powers that be. It's possible, but I would say not likely.
I go back to one of my old saws. Violence does indeed solve problems. Brutality is useful. Opponents are eliminated, intimidated, dispersed, etc. Sure, their political will may not be extinguished and may even grow, but a succession of successful short-term remedies adds up to a permanent solution. Israel, for instance, may not enjoy peace, but from a military standpoint its position is pretty secure.
Will U.S. violence solve this problem? How should I know. I suspect it will be helpful. Better to have the OBL network on the lam, hiding in caves than ensconced in more secure settings where they can do more dirty deeds. Better to turn their facilities, rudimentary though they may be, to powder. Better certainly to have the world's security services focusing on al-qaida and its money than not (toughening money tracking laws in the process). Better to have several hundred suspects in the pokey than running around. Some of them undoubtedly are innocent, but we're talking practicality now, not ethics or democracy. A lot of innocents will die, and more terrorists will be generated. The question is whether more attacks can be precluded. CC's criteria. I think he's wrong, but we will know the answer relatively soon. If the answer to U.S. violence is no further incidents on the scale of 9/11, I think we'd have to say it served its purpose. Perhaps not in the best way, nor with the best of motives, but those are secondary. More than secondary would be the result that, more than ever, the public is reminded that the Left is not fit to rule. It can't figure out something as simple as public safety. How could it be qualified to remake society?
mbs