A couple of points:
First of all, I'm not sure "pure" altruism is achievable outside an individual act or that of a relatively small group. An organization with the size and complexity of a military force cannot accomplish anything out of "pure" altruism. In even the most benign actions there is always someone who benefits, from the owner of the company that makes munitions or other military supplies down to the cashier at the base PX. However, there are many altruistic acts within the action itself. The soldier who shares his rations with a poor family, the unit that stands and fights to prevent a massacre of innocent civilians when it could retreat and avoid casualties, the pilot who exposes himself to greater danger in order to minimize collateral damage. All of those and more are examples of altruism that occur in war.
Secondly, whoever said that a humanitarian or protective missions have to be 100% pure altruism? As the DUmmies are so fond of saying, "We can't police the world." We have limited resources and it makes perfect practical and moral sense to allocate those resources in ways that protect both the interests of the subject country and those of the U.S. populace. That could mean anything as basic as requiring agreements that the country stay on friendly terms and not to allow terrorist elements to set up camp there to trade agreements that allow us to help them develop their natural resources in a mutually advantageous way. As long as that nation is left with a democratic system that lets the people choose their leaders and how to proceed with future relations with us it could not be considered imperialism. Why would we expend our national blood and treasure helping a country that is, could turn into, or supports those who are, our sworn enemy?
Those countries already receive plenty of moral support from individuals like one finds at DU.
