Moral relativism is a stance that is popular in some (particularly academic) circles, but a little thought demonstrates how problematic a position it is to defend. According to moral relativists, there is no objective moral truth, only truths relative to social, cultural, historical, or person circumstances. However, the moral relativist now has to swallow some pretty unpalatable conclusions, or else explain why they cannot legitimately be deduced from the premises of moral relativism. For example: slavery was morally right in the American Deep South; killing Jews was morally right in Nazi Germany; the Stalinist purges were morally right in Communist Russia; the inclinations of certain US leaders to impose their views upon other countries by force is morally right for them; oppression of women in Iran, Saudi Arabia, and Afghanistan is morally right for them.
In fact, if we dig a little deeper here, we can expose some more problems with moral relativism. Firstly, how exactly do we determine the society, culture, or group that the morality is true for? For example, we might suppose that oppression of women is moral in Iran, but how about the women being oppressed – don’t they count in our calculations? In fact, culture and state is a transient and mutable thing – a set of traditions, religious and political ideologies, and individual, tribal and group power struggles. If a culture or state is oppressive, patriarchal, or tyrannical, there is no reason why its citizens should be forced to endure it. We are defining the correct morality for that society based upon what the powerful wish to impose upon the less powerful. It should be further borne in mind that nobody chose to be born into a particular culture and state. It was purely chance that governed where they were born, and they shouldn’t be condemned to a miserable life under some totalitarian regime because of this.
Following on from this, defining the correct morality in terms of the society or culture has the effect of rendering morally wrong anybody fighting for moral change within that society. So, according to this view, the (slavery) abolitionists were wrong since they were fighting against the accepted societal morality, and the suffragettes were wrong, as they were fighting against accepted societal morality etc. In fact, it would seem that only a non-relativist can be truly tolerant, since they can hold it as an objective property of any good morality that tolerance must be enshrined. By contrast, the relativist has little choice but to accept intolerance as moral for any society in which it is normative. A point usually lost on relativists is that if our morality is such that we wish to impose universal freedom and equality upon other societies, then that morality is true for us.
I think that these examples expose moral relativism for the absurdity that it is. As a system of ethics, I don't think that it gets off the ground. The moral relativist and I would concur that there is no absolute moral truth. However, I would go on to reject the idea that moral truth exists in a relativistic sense either. Nevertheless, in the absence of an absolute moral truth, I believe that, under almost any rational definition of morality, it is still possible to say that some moral systems are better than others. Hence, our task is to discriminate between the possible candidates, and try to determine what characteristics a moral system should possess in order to be a good one. Oppression, intrinsic inequality, and support for wholesale slaughter of the innocent are unlikely to be part of any such good system, and should not be excused because they are present in some other society or culture.
In the past, Westerners have tried to impose upon others by force systems of morality that have left much to be desired (they have usually been religious moralities). This was wrong, but it doesn't mean that we are now wrong to judge bad moral systems in other societies.