Given that we don’t all value exactly the same things and don’t all order our values in exactly the same way, morality is always underdetermined and contestable. Given that we value (disvalue, fear, etc.) a lot of the same things, morality and social life are possible.

Russell Blackford at Metamagician and the Hellfire Club has written an excellent post about what he calls naturalistic moral pluralism. His thoughts reflect my current views very closely. He just says it better than I do.