Contrary to some haters, altruistic acts that benefit others at costs to oneself are indeed possible and real. But altruistic acts do not necessarily accrue benefits to all others. Instead, they usually are done to benefit one's own in-group. One extreme example of this "dark side" of altruism is suicide bombing, as explained by Robert Pape and summarized briefly here.
What this underscores is that altruism is not necessarily laudable and can be dangerous in the absence of cosmopolitanism. And in general, I think that altruism + cosmopolitanism = preference utilitarianism. So most of the "good" usually discussed regarding altruism can be "explained away" by the preference for max utility.
