Does common sense morality assume objectivity? According to a recent study by Goodwin and Darley, most folk actually don't believe that their moral judgments are objectively true.
It's not clear how this fact is any response to the question. The question, recall, is not whether most folk believe in moral objectivism (which is all the survey can tell us). That's quite irrelevant. The real question is whether our moral practices rationally commit us to objectivism, and that is not a purely empirical question. It's a normative question, so there is simply no way to answer it without actually doing philosophy.
I don't mean to bash all attempts at empirically informed philosophy. If we are concerned with analyzing actual moral practices, it's an empirical question just what those are, i.e. what moralizing behaviours people in our society engage in. It's entirely appropriate to use empirical data as a starting point for philosophical inquiry, especially if that data is precisely what we're wanting to analyze. My point is simply that empirical work cannot substitute for philosophical analysis.
Further, it will rarely be worthwhile to ask folk for their theoretical opinions. Surveys like the above merely tell us what pop-philosophical theories are most prevalent in our public culture at present. Many people will profess a belief in relativism, for example, even if further probing would eventually reveal that they don't actually accept the implications of this view. As R.M. Hare once wrote:
If we want to find out what ordinary people mean, it is seldom safe just to ask them. They will come out with a variety of answers, few of which, perhaps, will withstand a philosophical scrutiny or elenchus, conducted in the light of the ordinary people's own linguistic behaviour (for example what they treat as self-contradictory).
So, next time you come across a study reporting the philosophical beliefs of non-philosophers, just remind yourself of the classic Onion study: