I would say that Robert M Pirsig made a pretty good case for objective morality with his Metaphysics of Quality. I had never agreed with the notion before (usually the arguments are religious in nature and require faith to accept) but it is the closest I've ever come to accepting objective morality as brute fact. At the very least it is compelling to indulge in and try out, can't say I've ever looked at things in quite the same way since I first finished Lila.