Ethical disagreement and ethical anti-realism

For one of my classes, I've been reading John Doris and Stephen Stich's Stanford Encyclopedia article "Moral Psychology: Empirical Approaches," and in particular the section "Moral Disagreement". They offer the following argument against moral realism/ moral objectivity (they use both terms):

(P1) If morality is objective, then [all?] moral disagreements will decrease over time.
(P2) Many moral disagreements do not decrease over time.
Thus, morality is not objective.

In support of (P2), they point to Nisbett's interesting findings about differences between non-latino whites in the Southern U.S. vs. in the Northern U.S. on the subject of when and to what extent force is justified. Very roughly, Southerners think violence is warranted and excusable in a wider range of cases than Northerners (if you aren't familiar with Nisbett's data on this, it's fascinating; Doris and Stich do a great job of summarizing and explaining it). Another example in support of (P2) is that Western Europeans and East Asians respond (on average) differently to the 'magistrate and the mob' thought-experiment: Westerners are more likely to say that an innocent man should be set free, even if setting him free leads to a riot killing many people. Their final example is Hopi attitudes about harming animals.

Doris and Stich recognize that most realists will direct their criticisms at (P1): disagreement can persist because people are selfish, biased, or unaware of certain things -- but if we were all disinterested, unbiased, and fully informed, then disagreements would eventually vanish.

I was wondering about another type of reaction to their argument. I wonder whether we could say that, for some moral disagreements, there is a fact of the matter about whether one side is right and the other wrong, whereas for other moral disagreements, there is no fact of the matter about which side is correct.

Perhaps this is conceptually incoherent, and a 'sometimes objective, sometimes not' position is unworkable. But I think it is intuitively appealing in some other cases, such as athletic merit. For example, think about the question 'Who is the best baseball player in the world?' I think it's defensible to say that there is no fact of the matter about this question. There will be a fact of the matter for various more specific questions, like which professional player had the most home runs this year. But since different players have different strengths and weaknesses, and because there are different demands on different positions, there is no fact of the matter as to which one person is the best player. However, there is a fact of the matter about whether Albert Pujols is a better baseball player than I am.

What's going on here? It seems to me that there are a number of dimensions or variables we use when evaluating a baseball player. At the most coarse-grained level, these variables would be the ability to hit, throw, and field. Now, Pujols is much better than I am at all three; that is why he is better than me period. But if one person is not better than the other on all three, then it will matter how we weight the different variables, and (I'm thinking) that there is no fact of the matter as to the unique correct weighting of the various variables.

It could be that something similar is going on in the three ethical examples of disagreement Doris and Stich present. In each of these three, there are various ethical principles in play, that could be weighted differently, and there is no fact of the matter as to exactly which weighting is the right one. In the case of the Magistrate and the Mob, utilitarian (and/or communitarian) principles conflict with a fairness principle. Now, everybody agrees that other things being equal, we should not punish the innocent, or choose a greater harm over a lesser harm. But those two ceteris paribus principles conflict in this case.

Perhaps a similar (if not identical) account could be given in the Northerner/ Southerner case: most people agree that most transgressions should be punished. But which transgressions, exactly? -- And how much punishment, exactly? Everyone who punishes must balance justice against avoiding cruelty. Alternatively, this case might be better understood as an instance of vagueness -- but many people (but not epistemicists) believe that there is no fact of the matter concerning whether a particular borderline patch of red-orange really is red.

So in short: some ethical claims are objective, and some are not, just as some claims about who is a better baseball player are objective and others not.

I am not an ethicist. Is this proposal already out there in the literature? (Ted Sider has an article "Hell and Vagueness" that discusses cases of borderline ethical goodness, but does not address the objectivity of morality.)