Heretical thoughts are nice, so here’s one: why should the death of a volunteer soldier be more outrageous than the death of a fisherman (sexist?), a coal miner, or, poignantly, a private security contractor? Everyone admits that the premature death of a human being is tragic, but the outrage expressed toward the government in this case goes beyond that. The sentiment seems more like what you would expect if a police officer were to shoot and kill someone needlessly. It is as if the state has put these men and women in harm’s way against their will. What about their role in it? They signed up.
However, after joining the armed forces, a soldier is forced to stay for a period of time, and there’s where I can see a basis for outrage. In particular, I could imagine that some individuals who entered the military before 2003 would have chosen not to do so, had they known that the US would soon be engaged in deadly low-intensity warfare for a number of years in Iraq. Though it is commonplace to work under a contract, you can’t sign away your liberties, except in the case of the military (and perhaps some other government organizations?).
It’s pretty obvious why deserting is harshly punished — many would leave whenever a war started. This might not be undesirable as a deterrent to adventurism, but the same effect might be seen even in situations where everyone agrees that the nation needs defending. If another large power were to invade, a soldier might reasonably expect that getting killed or injured is likely, enough so that the state could almost not offer enough money to compel the solder to stay (neglecting the effect of patriotic sentiment and/or “guns are cool”). If you figure a job has a 50/50 chance of getting you killed, would you take it for any price? Maybe you would if it meant that your kids would get a bunch of money and be taken care of after you die, but you might well doubt the credibility of such a promise when an invasion is imminent. Not fighting makes it more likely that the invasion will succeed (an tremendously costly event for the individual) but only by a tiny amount. One soldier less will not much hurt the war effort. So you have to weigh maybe getting killed against making it a tiny bit less likely that the invasion will succeed and getting paid some amount of money. Clearly, many would choose to avoid getting killed. It’s a Prisoner’s Dilemma type problem.
Ideally, all the potential soldiers would agree to either all fight or not. Then the individual’s choice is maybe getting killed and perhaps repelling the invasion versus refusing to fight and being occupied. Depending on the situation, this choice could go one way or the other. Certainly, citizens would fight for their country if the invader will probably dismantle existing social institutions and abuse them. Conversely, I suppose in many countries the citizens might not mind being occupied by the US, if it meant more effective government, no trade barriers, and the right to work in the US.
But such an agreement among all potential soldiers doesn’t appear to be feasible, so the government solves the problem using force. Resisting the invasion is assumed to always be the most socially beneficial course of action, though it might not be.
So, getting back to the point, there is a reason to be outraged about troop deaths (in a political sort of way) when the state uses the armed forces to wage war needlessly, even if entering military service is voluntary, because exiting is not.