[yummyfajitas]

In basically all cases I can think of, forcing people to buy private goods (rivalrous and excludible) is harmful to the people who would not otherwise choose to purchase those goods.

Your example of bombs/military spending doesn't fall into that category, since defense is neither rivalrous nor excludible. My enjoyment of Iraqi deaths does not hinder your enjoyment of same, and the military has no way of preventing me from enjoying Iraqi deaths if I don't pay my military bill. Thus everyone has an incentive to freeload and a free market will not allocate enough resources to killing Iraqis.