Cultural or subjective relativism claims that there are no universal, trans- subject or culture moral principles. That what is ethically right for one subject or culture, might not be for another. Likewise, what is wrong for one subject or culture, might not be for another.
But, ask any relativist you know whether s/he thinks genocide, rape, pedophillia, etc., is wrong, immoral, bad, you'll no doubt here something like: "Well, I think it is." Or, "Well, our culture says it is."
Besides the many, many problems for any form of ethical relativism, I'd like to raise another I recently thought of.
Given the truth of ethical relativism, it seems highly probable that other subjects or cultures would use its truth to justify what you or your culture takes to be immoral.
This isn't speculative either. Take Bundy:
Then I learned that all moral judgments are “value judgments,” that all value judgments are subjective, and that none can be proved to be either ‘right’ or ‘wrong.’ I even read somewhere that the Chief Justice of the United States had written that the American Constitution expressed nothing more than collective value judgments. Believe it or not, I figured it out for myself – what apparently the Chief Justice couldn’t figure out for himself – that if the rationality of one value judgment was zero, multiplying it by millions would not make it one whit more rational. Nor is there any ‘reason’ to obey the law for anyone, like myself, who has the boldness and daring – the strength of character – to throw off its shackles…. I discovered that to become truly free, truly unfettered, I had to become truly uninhibited. And I quickly discovered that the greatest obstacle to my freedom, the greatest block and limitation to it, consists in the insupportable ‘value judgment’ that I was bound to respect the rights of others. I asked myself, who were these ‘others’? Other human beings, with human rights? Why is it more wrong to kill a human animal than any other animal, a pig or a sheep or a steer? Is your life more to you than a high’s life to a hog? Why should I be willing to sacrifice my pleasure more for the one than for the other? Surely you would not, in this age of scientific enlightenment, declare that God or nature has marked some pleasures as ‘moral’ or ‘good’ and others as ‘immoral’ or ‘bad’? In any case, let me assure you, my dear young lady, that there is absolutely no comparison between the pleasure I might take in eating ham and the pleasure I anticipate in raping and murdering you. That is the honest conclusion to which my education has led me – after the most conscientious examination of my spontaneous and uninhibited self. Louis P. Pojman The Moral Life: An Introductory Reader in Ethics and Literature (Oxford University Press: 2003).
Or take another example from history. Nazi war criminals defended themselves by claiming that they were just following orders given by their culture and legal system. In response, Robert Jackson, chief counsel for the U.S. at the trials responded by saying that: "there is a 'law beyond the law' of any individual nation, permanent values which transcend any particular society."
It seems, then, that, for some, the truth of ethical relativism, for them, will serve as an excuse for them to do things that you, another relativist, thinks is wrong.
Thus, your teaching relativism may lead to people commiting crimes that you take to be highly immoral. That seems highly counter intuitive a result for an ethical theory to produce. Usually we think teaching ethical principles will have the opposite effect. People will be "better" (according to our created standard of better).
Thus it may better to not teach relativism but to teach some kind of ethical absolutism or ethical objectivism where the ethical principles that are absolute or objective transcend subject and culture instead.
The relativist might respond that that would be lying and s/he (or the culture) believes lying to be wrong. But why not allow lying in this instance? Most do not believe it would be wrong to lie to the Nazi at your door step, so what is so wrong about lying about what ethical theory is correct, especially when people might use it to justify henious acts that you take to be highly immoral? Wouldn't it be worth it in this instance to lie?
Another response might be: But teaching relativism is needed because we need tolerance, tolerance among people and cultures would make them less likely to commit genocides, exercise racism, etc. So, teaching relativism will, hopefully, lead to a lessening of genocides &c. Thus my ethical theory will promote what I take to be morally right.
But here the relativist imposes her morality on others. The relativist believes she is right and others are wrong. She is saying with this claim that: what I or my culture thinks is right for us, is right for everyone. Just because the relativist thinks we should be tolerant, doesn't mean another relativist won't use that to his advantage, claiming he doesn't need to be tolerant.
These people could commit what the relativist takes to be highly immoral atrocities. There would be more ground to convince the person or others that he is wrong by claiming a (limited) tolerance is an objective ethical principle, not made true by subjects or cultures beliefs. So, the tolerance principle would still get taught.
Since most ethical relativists will think it is okay to lie in instances where telling the truth could have very disasterous consequences, then it wouldn't violate immoral instances of lying. To tell the truth would, actually, be immoral.
It seems to me that many relativists should think it immoral to teach relativism.