Over on Environmental Economics, J.S. writes (in Self Interest is the Answer),
There are many people who are motivated to protect the environment (or promote human rights or other progressive activities) because of a deep sense that it is the right thing to do. These are the type of people who if confronted with a situation where they had to risk bodily harm to save a fellow creature would do so not because of any desire for reward or material gain, but because they couldn’t imagine not doing so. They have incorporated a sense of compassion and integrity into their conception of their self-interest to such a degree that they couldn’t live with themselves if they didn’t act in ways that reduced suffering in the world. This perhaps is the highest form of self-interest, but it is self-interest nonetheless, albeit a highly evolved form.
That is a really convoluted argument. Altruistic behavior is altruistic, not a highly evolved form of self-interest. If people engage in behavior with a net negative benefit to themselves, e.g. altruistic punishment, why call it self-interested? It is not. Altruistic punishment promotes cooperation and does a lot of good. You may feel good about engaging in it, but it is still altruistic.
And as Adam Smith said in The Theory of Moral Sentiments,
“How selfish soever man may be supposed, there are evidently some principles in his nature, which interest him in the fortunes of others, and render their happiness necessary to him, though he derives nothing from it, except the pleasure of seeing it.”