Stipulate, purely for the sake of argument, that Americans do have some collective obligation to prevent suffering elsewhere in the world, and that this obligation is properly met, at least in part, via government. (Perhaps because governments are uniquely able to remedy certain kinds of suffering—such as those requiring the mobilization of a military.) Given that we have finite resources, surely the worst possible way to go about this is by making a series of ad hoc judgments about particular cases—the "how much do I care about Steve?" method. The refusal to consider whatever global duty we might have holistically is precisely what leads to irrational allocations—like spending billions to protect civilians and rebel troops in Libya when many more lives would be saved (again, let's suppose for the sake of argument) by far less costly malaria eradication efforts. Unless there's an argument that we have some specific or special obligation to people in Libya—and I certainly haven't seen it—then any claim about our obligation to intervene in this case is, necessarily, just a specific application of some broader principle about our obligation to alleviate global suffering generally. The suggestion that we ought to evaluate this case in a vacuum, then, starts to seem awfully strange, because if we are ever going to intervene for strictly humanitarian reasons (rather than to protect vital security interests), then the standard for when to do so has to be, in part, a function of the aggregate demands whatever standard we pick would place on our limited resources.