Well, last time I wrote here I was talking about moral relativism, and I brought up the idea that you can do whatever you want, as long as you don't either (1) impinge on someone's freedom, and (2) hurt anyone. I was trying to make the point that there are problems with (1), because freedom could be an absolute standard and because how do you know you "shouldn't" impinge on someone's freedom unless that is given from a higher standard?
But what about hurting someone?
Let's return to the example of the man who raped your little sister. How do we know it's wrong? There are two views to this. First, if there are moral absolutes, then the rape itself is wrong. No matter who I am, if you ask me if the rape is wrong, no matter what I answer, the rape is still wrong. (In other words, I could say the rape isn't wrong, and I would be incorrect.)
On the other hand, if you're a relativist, then the rape is no longer wrong. It is only up to the observer to choose whether it is right or wrong. If you ask me if it was wrong, then I would say it's wrong, OR I could say it wasn't; in either case, I would be correct. The rightness or wrongness of the action doesn't have to do with the action, it only has to do with whom your are asking. No one has a privileged opinion.
Michael Shermer (a moral relativist and founder of Skeptic magazine) would say that we need to ask the girl whether the rape is wrong. Ok, so let's ask the girl her opinion on whether the rape was wrong. I have no doubt she'd say yes, it was wrong. So does that settle it? She says she was hurt, therefore the rape was wrong?
But if there are no moral absolutes, then again, no one has a privileged opinion. In other words, we would be just as accurate to ask the rapist whether he thought the rape was wrong. I'm not a criminal psychologist, but I get the feeling that he'd say it was wrong, too. But let's just say for the sake of argument that he said it wasn't a wrong thing to do. Now where do we stand?
Well, we could bring him to court, since the girl or her family would probably press charges. Then it's up to the jury to decide (based on the evidence at hand) whether the rapist should be punished. But again, if there are no moral absolutes, then no one has a privileged opinion. Why should the jury be allowed to decide that it was wrong if we're supposed to be able to decide what is right and wrong for ourselves? Sure, you could claim the guy hurt the girl, and that's why he should be punished, but what if he says she's lying and that he didn't hurt her? And why in the world, if there are no moral absolutes, can we say you shouldn't hurt someone?
In summary, if you're a moral relativist, then metaphysically you have no power to stand in judgment over someone who has committed a crime. The jury cannot decide, the judge cannot decide, the police cannot decide, and the family similarly has no moral highground to stand on to judge this man's actions.
The answer that most people give to this seeming absurdity is that, as a culture, we define our own morality. So, sure, no moral absolutes exist, but for the good of mankind and the good of the culture, we have decided to enforce some rules, and one of them is you shouldn't rape someone. That's why a jury of twelve peers should be able to make a decision on this: it's a sufficient cross-section of our society to come together and decide what our culture's point of view is on such a case.
But when you carry that to its logical end, even that doesn't make sense. More on this later.