Let's pan back a bit, just to get perfectly clear: The issue is whether Taliban fighters and/or al-Qaida terrorists held by the United States at Guantanamo can be classified as prisoners of war under the Third Geneva Convention of 1949 (and thus accorded certain legal rights and privileges), or whether they are to be classified as "unlawful combatants" falling outside the protections of the Geneva Convention. Today it looks like the administration will split the baby—say they are protecting the detainees under the Geneva Convention while declining to give them POW status. This is no less intellectually silly than being at war without ever having declared one, but I am getting used to the suck-and-blow philosophy with which the Bush administration runs its wars.
This morning's Times makes it clear that even the Bush administration is fast abandoning the position you're espousing—that the Geneva Convention simply doesn't apply to these detainees. This is for pragmatic and international-relations reasons, but—as you point out—the administration's been pretty darn candid that it's mostly because they forgot to look at the law before issuing proclamations about the status of these "prisoners—or detainees, excuse me" to quote the president.
You have offered what looks to be a principled bright-line test for whether the detainees are POWs or something else: The Geneva Convention should never be applied when the combatants in question target civilians. (You'll correct me if I've oversimplified). It begs the question, Scott, don't mostwars—or many actions in many wars—ultimately target civilians? Americans have deliberately targeted civilians plenty of times (Dresden, Hiroshima, and Nagasaki …). Under your analysis, the Dresden pilots, if shot down, wouldn't have qualified for the Geneva protections.
Certainly, if as you say, the whole purpose "of the rules of warfare is to protect noncombatants," then parties targeting noncombatants might be exempt from the rules of warfare. That is, I believe, a tautology. But from where do you derive the notion that the primary object of the Geneva Convention is to protect civilians? I don't find a statement of such a principle in the convention itself. No, I'm not a strict constructionist, but I do believe that you can derive great insight from the title of a law, and the clear intention as stated in the title of the third Geneva Convention is to protect combatants.
There is something too ironic—even for me—in the assertion that the laws of war ("wars" today being those things in which thousands of civilians often get killed) exist principally to protect civilians. I think you're balking at the truth, which is perhaps even more ironic: The laws of war exist to ensure that while we're ripping one another's faces off, we're comporting with some minimum standard of human decency. It's such a counterintuitive notion that it's easier to define it away. Still, this is the other plausible explanation for why we "make a fuss about uniforms, insignias, and the open display of weapons." We are trying to differentiate between honorable and dishonorable ways of ripping each other's faces off.
Your argument, and Rumsfeld's, is that terrorism is a quantitatively more dishonorable way to rip each other's faces off. But you have to answer two fundamental questions for me: Why would the rules of war draw such a distinction? And more important for the question before us, why should we act dishonorably in response?