It's all relative?

This essay by Jesse Prinz looks like a useful defense of moral relativism to have students read if you teach ethics. But it's a bit shocking. Let me count the ways:

1. Prinz points out that different cultures have different morals and that opponents of relativism deny that this makes relativism true. After all, different cultures have different scientific beliefs too, but we don't say that these beliefs are all equally true. Prinz rejects this response, though, because "morals do not track differences in observation, and there also is no evidence for rational convergence as a result of moral conflicts." So ethics is not science, and the analogy between scientific disagreements and ethical disagreements breaks down at some point. It hardly follows that it never gets going in the first place.
2. "Moral variation is best explained by assuming that morality, unlike science, is not based on reason or observation. What, then, is morality based on? To answer this, we need to consider how morals are learned." Isn't this a mistake about the meaning of "based on"? We get our morals from our parents, peers, preachers, and so on, at least for the most part. (It is also possible to innovate, to carry on a tradition, rule, or practice in some unexpected way, but this is rare.) But people who say that morals are based on reason surely do not deny this. They mean, I would have thought, that good morals can be given a rational justification. To see whether this is true we need to examine the alleged justification and see how rational it is, not consider how morals are learned.
3. "Morality involves specific emotions." This is probably true, but I flag it because it sounds dangerously close to Hume's idea that moral approval and disapproval are specific inner objects that we identify with an inner sense. (At least I think Hume's view is something like this.) This is a bad theory.
4. "If this picture is right, we have a set of emotionally conditioned basic values, and a capacity for reasoning, which allows us to extend these values to new cases. There are two important implications. One is that some moral debates have no resolution because the two sides have different basic values. This is often the case with liberals and conservatives." This might be true, but a) it isn't relativism, and b) I'm not convinced that liberals and conservatives admit to having very different values. It isn't relativism because relativism says that both sides are right, not simply that it might be impossible to reach an agreement. As for political disagreements, some are based on differences in knowledge (if you choose to get your news from people who like to suggest that Obama is a Kenyan, Muslim, communist then you might end up disagreeing with others for flat-out bad reasons, not because of different basic values), some are based on prejudices that the people who have them are ashamed of. Racism comes to mind, but perhaps hatred of the rich or envy of the successful might be a factor too. But few conservatives will happily say, "Yes, I'm racist, and that's just a basic value difference between us," just as few liberals will happily say, 'Yes, I hate rich people, and I want to punish them even if doing so helps no one." There are basic differences, I agree, but the differences that we are prepared to admit to, that are not guilty secrets, are rather few and small, I suspect.
5. "The second implication is that we cannot change basic values by reason alone." Agreed. But, again, this is not relativism.
6. "The hypothesis that moral judgments are emotionally based can explain why they vary across cultures and resist transformation through reasoning, but this is not enough to prove that moral relativism is true. An argument for relativism must also show that there is no basis for morality beyond the emotions with which we have been conditioned." No. The basis for morality is irrelevant. As Prinz says at the start of his essay, relativists "believe that conflicting moral beliefs can both be true." An argument for relativism must show that this is a good belief to have. But can we believe that "It is good to eat the bodies of one's foes" is both true and false, true when asserted by a cannibal from a cannibal culture and false when asserted by someone like me? I don't think we can believe this, unless we use 'true' in some technical sense, meaning something like 'sincerely uttered.'
7. "the problem with Hitler was not that his values were false, but that they were pernicious. Relativism does not entail that we should tolerate murderous tyranny. When someone threatens us or our way of life, we are strongly motivated to protect ourselves." But relativism does entail that when Hitler says "Jews are inferior" what he says is true (and that this is false when said by most other people). Why should we accept this? It isn't remotely acceptable.
8. "Allegation: Relativism entails that moral debates are senseless, since everyone is right.Response: This is a major misconception. Many people have overlapping moral values, and one can settle debates by appeal to moral common ground. We can also have substantive debates about how to apply and extend our basic values. Some debates are senseless, however. Committed liberals and conservatives rarely persuade each other, but public debates over policy can rally the base and sway the undecided." This is close to a point I tried to make above. But the fact that committed liberals and conservatives rarely persuade each other does not mean that what both sides say is true. 

Having said all that, I wonder now whether this would be good to give to students. Perhaps they could be challenged to find at least half a dozen errors in it. Or perhaps it's better than I think.