People are motivated to follow happiness and flee from pain. These feelings *exist* to color our memories with our physiology so that we may extract meaning our experiences. It's a tautology to say that people do what makes them happy -- despite this, one often sees claims that there exist no altruistic acts, because such actions are the end product of people trying to maximize their happiness. This is to define aultrism out of existence, remove a useful word with which to partition our observations of reality. Instead, we may say that some people's happiness is bound up with other people's happiness and these people should be supported because of the obvious common cause with our own feelings.
A weaker form of the conservative argument (not mentioned here) is that a portion of seemly altruistic acts are covers for the fear associated with guilt.
When my eyes see phrases like 'right thing to do', 'appropriate' etc, I wonder what unstated world view I am meant to share. These phases smell of that unusually putrid whip; social sanction. But every man has experienced social sanction as the direct manifestation of morons baying at the moon, nodding and calling the result consensus.
Here, in Africa, there was a two page fold out on the "Night Runner" plague. Plague? Yes. Of people -- typically old, who supposedly run around naked at night (remember the population has pitch black African skin tones), tapping on windows, throwing rocks on peoples roofs, snapping twigs, rustling grass, casting spells and getting lynched because it's "the right thing to do".
Insofar as we can affect the world, let it be to utterly eliminate guilt and fear as a motivator of man and replace it cell for cell with love for one another and the passion of creation.