Cultural relativism, applied to morality, is the notion that what is right and wrong is entirely determined by which culture the people involved belong to. This is a natural position to arrive at, after seeing that people in different parts of the world believe differently about morality, but it’s also been pointed out that it has the problem of not making any sense.
The biggest problem that makes cultural moral relativism contradict itself is that when different cultures have different views about what’s morally wrong and right, this means that they contradict each other, and this in turn means that they contradict relativism. If culture A says that sex outside of marriage is acceptable and culture B says that it is not, what does relativism say? You might try saying that it says it’s all right if you’re in culture A but not if you’re in B — but that contradicts both A and B at the same time. Certainly it’s true that there are some cultural beliefs about morality that say that if you’re in this culture, then you must follow a certain rule, but outsiders can ignore it. Most moral beliefs aren’t like that, though. Imagine a modern western person saying “Killing people is forbidden for those who belong to my culture.” It seems cultural relativism can’t say that both moral beliefs are actually correct at once.
I could mention that there are other problems with cultural relativism that could have a huge practical effect — such as that, in saying the norms of another group are to be accepted, you will also accept any norms that oppress people within that culture, be it women in a traditionalist society or black slaves in America in the past. However, there’s nothing logically wrong with this. It only comes from trying to import universalistic moral notions into what was supposed to be a relative scheme. If we take the statement of moral relativism at face value, then slavery is right if the culture believes so, period. (You may be detecting some irony in the way I’m discussing this. If not, start doing so.)
The first problem, however, creates a clear internal inconsistency. What is moral relativism even telling us to do when cultural views clash? I will now show that this follows from another inconsistency, an assumption that should not be made in the first place.
The problem stems from assuming that the moral relativist stance itself is a moral absolute. But of course it’s not. According to itself, it’s not. It’s a moral view, and thus it can only be the moral view of a certain culture, in this case some moral philosophers.
The relativist cultural moral view is unique in that it’s the only one that encourages not taking any sides or trying to change any other cultural moral view. Normal moral views imply that they should be followed universally. According to the relativist view, consistently seen, whatever happens to be in the culture is all right.
Not understanding the above has also led to a common misconception about moral relativism, which is that western cultures should tolerate alternative moral views. On the contrary, according to relativism, western cultures should be somewhat intolerant even of people who belong to different cultures, no matter what they actually do. This follows directly from the facts that western cultures are intolerant like that. Of course, it’s usually only an implicit norm… so we shouldn’t actually say that since saying it is not the norm. We should claim to be mostly equitable but be so only sometimes. According to relativism, anyway.
There’s still a problem left in that each normal culture’s moral norms purport to be universal, meaning that they should override those of other cultures. This can be solved by analysing what the actual role of norms is (something that would deserve a longer and more serious discussion in its own right). The role of norms is to guide action. From this, we can give a formulation of cultural relativism that allows people who disagree about morality to be morally right at the same time: It’s always right to take actions that are right according to your culture (further your culture’s moral values). So, for example, ISIS is right to be doing what it does to further its idea of what’s right, and those who disagree and are fighting it are also right to do so.
To sum up the main point: Cultural moral relativism can be made consistent by affirming that it’s right for everyone to do whatever their cultural moral norms dictate, even when they are trying to stop others from doing whatever theirs dictate.
Thus, we see that while it seems that while it can be said that cultural moral relativism has some crazy consequences, formulating it properly shows that it can be said to have almost no normative consequences whatsoever, with most things just being deemed right by default. We can also see that while it’s usually seen as being inconsistent and having weird consequences, it can also be made consistent, which makes its consequences even more idiotic.
As a final note, I’d like to point out that I’m aware I cut many corners in terms of discussing this philosophically. There’s even a second inconsistency almost as big as the first one that I didn’t mention.