Let me respond with an excerpt from this secular philosophy textbook. This took aaages to type out, so please consider it. Towards the end it contains the funniest sentence I’ve ever read in any textbook ever (I’ve put it in bold).

The first thing we need to notice is that at the heart of Cultural Relativism there is a certain form of argument. The strategy used by cultural relativists is to argue from facts about the differences between cultural outlooks to a conclusion about the status of morality. [Which you did]. Thus we are invited to accept this reasoning:

1) The Greeks believed it was wrong to eat the dead, whereas the Callatians believed it was right to eat the dead.
2) Therefore, eating the dead is neither objectively right nor objectively wrong. It is merely a matter of opinion that varies from culture to culture.

Or, alternatively:
1) The Eskimos see nothing wrong with infanticide, whereas Americans believe infanticide is immoral.
2) Therefore, infanticide is neither objectively right nor objectively wrong. It is merely a matter of opinion, which varies from culture to culture.

Clearly, these arguments are variations of one fundamental idea. They are both special cases of a more general argument, which says:

1) Different cultures have different moral codes.
2) Therefore, there is not objective “truth” in morality.
…
But from a logical point of view, is it sound?

It is not sound. The trouble is that the conclusion does not follow from the premise-that is, even if the premise is true, the conclusion still might be false. The premise concerns what people believe… the conclusion, however, concerns what really is the case. The trouble is that this sort of conclusion does not follow logically from this sort of premise.

Consider again the example of the Greeks and Callatians… Does it follow, from the mere fact that they disagreed, that there is no objective truth in the matter? No, it does not follow; for it could be that the practice was objectively right (or wrong) and that one or the other of them was simply mistaken.

 

To make the point clearer, consider a different matter. In some societies, people believe the earth is flat. In others… people believe the earth is (roughly) spherical. Does it follow from the mere fact that people dis-agree that there is no “objective truth” in geography? Of course not….

Cultural Relativism proposes this argument, but unfortunately the argument turns out to be fallacious. So it proves nothing.

Do you consider our present attitude toward women better than that of those Iraqis? Do you consider our culture’s abhorring of such treatment of cats to be a better attitude than that of the past culture you mentioned?

For if you do, you are not a cultural relativist:

Suppose we took [cultural relativism] seriously. What would be some of the consequences?
1) We could no longer say that the customs of other societies are morally inferior to our own. This, of course, is one of the main points stressed by Cultural Relativism…. Cultural Relativism would preclude from saying that either of these practices was wrong. (We would not even be able to say that a society tolerant of Jews is better than the anti-Semitic society, for that would imply some sort of transcultural standard of comparison.
2) We could decide whether actions are right or wrong just by consulting the standards of our society…. Suppose in 1975 a resident of South Africa was wondering whether his country’s policy of apartheid was morally correct. All he has to do is ask whether this policy conformed to his society’s moral code. If it did, there would have been nothing to worry about, at least from a moral point of view.
3) The idea of moral progress is called into doubt…. Progress means replacing a way of doing things with a better way. But by what standard do we judge the new ways as better? If the old ways were in accordance with the social standards of their time, the Cultural Relativism would say it is a mistake to judge them by the standards of a different time… to say we have made progress implies a judgment that present-day society is better, and that is just the sort of transcultural judgment that, according to Cultural Relativism, is impossible.

So to accept CR is to reject any attempt to denounce the practices of another culture. It is to deny oneself the right to criticise the practices of one’s own time in the hope of progress. It is to lose any concept of moral progress over time.

If you want to retain the right to any of these, you must first renounce Cultural Relativism.

The final point I want to raise is the degree of actual differences between cultures. For:

Often, when we examine what seems to be a dramatic difference, we find that the cultures do not differ nearly as much as it appears.
Consider a culture in which people believe it is wrong to eat cows. This may even be a poor culture, in which there is not enough food; still, the cows are not to be touched. Such a society would appear to have values very different from our own. But does it? We have not yet asked why these people will not eat cows. Suppose it is because they believe that after death the souls of humans inhabit the bodies of animals, especially cows, so that a cow may be someone’s grandmother. Now shall we say that their values are different from ours? No; the difference lies elsewhere. The difference is in our belief systems, not in our values. We agree that we shouldn’t eat Grandma; we simply disagree about whether the cow is (or could be) Grandma.
… we cannot conclude, then, merely because customs differ, that there is a disagreement about values.

 

He goes on to show that Eskimos, who often kill perfectly normal infants, have the same values. It is not that they value human life less, but since they do value it, a pragmatic response to harsh conditions is required. They kill only when they must, and even then many other options are first considered. “I emphasise this in order to show that the raw data of the anthropologists can be misleading.”

He asks “Imagine what it would be like for a society to place no value at all on truth telling.” Can you think of one?

So, to sum up: the argument for CR is fallacious, its consequences are unpalatable (and inconsistent with your practice), and the differences seen in cultural values may appear greater than it actually is.

Then take the story I blogged about, that disgusting animal in Iraq that stomped his own daughter to death for being in love with someone he didn’t approve of – and the girl’s brothers helped murder her. That’s against OUR morals, because that sort of thing isn’t acceptable in a civilised society. Over there in Iraq? The guy was out of jail after TWO HOURS.

There are a few examples from the bible that in our society we wouldn’t accept, such as dragging unruly children to the city gates and having the men of the city stone them to death. Or making animal sacrifices, things like that.

There’s no absolute morality. If there was it would be universal, or at least a lot more widespread than it appears to be.