Today, Deity Shmeity talks about morality, and whether it's objective or subjective. He concludes that a moral standard is necessary, and says, "I define right conduct as simply that which benefits others more than it harms. Wrong conduct is obviously that which harms others more than it benefits."
Well put. It is possible that there is no objective right and wrong, in the grand scheme of things ("nature, red in tooth and claw" is predicated on harming others, after all, and like it or not we are part of nature), but in order for us to have a functioning society, there must be rules. And most truly sensible rules boil down to what is usually called the Golden Rule: "Do unto others as you would have them do unto you." Or as the Wiccan Rede puts it, "An it harm none, do what ye will." Heinlein touched on this concept with his usual bluntness: "Sin lies only in hurting other people unnecessarily. All other 'sins' are invented nonsense." The Golden Rule was not invented by Christianity, though Christians like to pretend it's exclusive to their religion; it has appeared time and again in numerous ethical traditions.
This rule allows an egalitarian society to flourish without too much conflict. Of course people will "sin" and harm others, because people are not perfect-- a point on which Christianity is correct, though to me thinking of people as born sinners who should all go to a fiery eternal damnation without Jesus' intervention is a bit much. But we all do wrong sometimes, even if our wrongs are only failing to return library books on time and occasionally parking in a loading zone, and this is why laws and punishment are necessary. It would be nice if our laws were based more on the Golden Rule, and less on silly religious ideas, especially as the latter often actively do harm people.