You're not getting my argument. When I say, "don't be ethnocentric", I'm not appealing to a universal moral standard; I'm appealing to what I thought was a shared value in our subculture. I have no delusions that the principle of avoiding ethnocentrism is some universally valid moral precept. --So when I see Japanese culture, 17th century, in which Europeans were considered primitives, I don't say "They are clearly inferior to us because they're ethnocentric"; I say "Based on my socialization, I don't share their ethnocentric worldview".
Perhaps the problem here is that people tend to assume that morals are only valid if they are universal, and any claim to the social production of morals and values is a rhetorical device to discredit those moral standards. To borrow from old whiskers, let's turn this on its head: it is only through social relations that morals are produced. Note this does not mean our morals are unimportant to us; it just means--they are important to us because social relations have made them important to us.
C'mon, how much more Marxist can you get?
Miles