Relativists inevitably make moral judgments. I don't say this pejoratively; I make moral judgments too. Everybody does! And that's the point. If the relativist thinks it’s wrong to judge, how can he say that those of us who claim that something is morally wrong are "mistaken" in the first place? Isn’t he just making a judgment by saying that and thereby pushing his socially conditioned view on me? Whenever a relativist says you shouldn’t force your views on others, the first words out of your mouth should be "Why not?" Any answer given will be an example of him forcing his views on you.
Relativism is not neutral. Some relativists claim that the attempt to enforce a point of view (i.e. to "legislate morality") on a controversial moral issue is illegitimate because that point of view is based on prior metaphysical commitment. As such, the government should not restrict it. But to say that government should remain neutral on metaphysical questions is a metaphysical claim -- a moral statement about how government should function. The fact is that most moral issues are controversial. So what? The fact that a point of view is controversial has nothing to do with the rightness or wrongness of the issue in question.
Moral relativism leads to inconsistent conclusions. Relativism doesn’t allow its adherent to claim anything is actually morally wrong, only that it is their preference to think it is morally wrong. This disallows the moral relativist the ability to advocate limiting moral wrongs if society has deemed them legal. Who is the relativist to question that? This illuminates the inconsistency in the moral relativist who claims on one hand that a moral position is wrong, while at the same time claiming adherence to moral relativism, which says that there is no such thing as an objective moral claim.
Moral relativism undermines the moral authority for cultural reform. Because most versions of relativism rely on the consensus of the community, many have actually promoted giving up on ethical disputes (against abortion for instance) because the issue we're arguing about is the law of the land, our challenging that law makes us sound "divisive," and our efforts are therefore an effort in futility. But legal does not equal moral.
Moral Relativism leads to absurd conclusions: Taking relativism to its logical conclusions is often a great way to show how utterly ridiculous it can be. Because the relativist cannot succumb to judging whether someone else's view is wrong, she will go to great lengths to remain neutral about it -- even in the face of such an obvious wrong as slavery.
we as a society today have reached a consensus that slavery is immoral. And while I do agree that slavery is abhorrent and wrong ... it is a view of morality that exists by consensus. Its place as unquestioned moral truth is perhaps less due to its correctness, and more due to the fact that "justice is the advantage of the stronger." If the South had won the Civil War, the way people look at slavery would certainly have evolved differently, and any discussion about the morality of slavery would look quite different.