Moral Relativism: A Critique

By moral relativism I mean the idea that moral norms are relative to some group of people, and that there is no moral norm that is superior to some other moral expression. Implication of such idea is that since there is no moral norm that is inherently superior to some other moral expression, one should be tolerant of other value systems and moral practices.

There is no disagreement that different societies express different aspects of  moral norms differently. Some people at certain point of history throw away deformed babies at dungheap while some people within that same society try to adopt these deformed babies discarded at the dungheap. Are these two practices equally honourable? Some people in certain society burn their daughter for marrying a boy outside of their society; while some people in that same period of history allow daughter to choose their spouse. Are these two moral expressions equally good? 

Our societies have got rid of slavery now.  We also have gone beyond owning gladiators. We do not burn the widows alive today (sati). Has there been moral progress? I think so. I do not suppose that one should say that we should be tolerant of those who own slaves or gladiators or burn widows alive. If indeed every moral expression is equally valid, then there is no way one can say that slavery or gladiatorial fight is morally wrong. But if we do say that they are wrong, it's because we judge them to be morally wrong from certain moral standpoint -- a higher level of moral standpoint.

Which moral expression is right or wrong is not always easy to decipher. But just because there are times when get confused, that does mean that every moral expression is equally valid. Some moral practices are evil. Rape, murder, theft etc has to be morally wrong. The fact that a society that considers them okay cannot really flourish, and this implies that there is incoherency in our human society when they are rampant. This implies that they must be morally wrong.