The basis of moral disagreement

You can download a short interview with Simon Blackburn at Philosophy Bites. It's about 14 minutes long and he's discussing moral relativism. Blackburn explains what this is and what he thinks is wrong with it: if it were true and moral disagreements were like differences of mere taste, people wouldn't care as much as they do about them. But in disagreeing they do care, and they argue as if something more than subjective preference is at stake.

At the same time, Blackburn says, he isn't a moral realist. He's not appealing to some moral reality - 'which [he says] is a rather mysterious kind of ontological denizen of the universe'. But he's arguing that moral differences often require, as differences of taste do not, practical resolution, determining how we are to live.

How is it, though, that without any moral reality of the sort the moral realist wants, argument about practical resolution of differences can go on as if this is real argument and not just the trading of subjective opinions?

A suggestion - my own and not from the interview - is that it can go on because of the fact (as it happens to be) that there are common moral standards, reference points, some of these all but universal. Even people with very opposed viewpoints will standardly appeal to the promotion of human well-being, the avoidance of harming the innocent or causing needless suffering; some things - conditions or actions - are experienced in nearly every cultural context as evils; and so forth. These common standards or reference points can be deployed in different ways. They don't necessarily lead people to the same moral conclusions in a particular case. But they form the shared framework of genuine argument, and that is why moral disagreement is different from expressing opposed preferences over flavours of ice cream.