I'm a very typical moral anti-realist but I still think humans have lots of values in common, that there are scientific ways to learn about those values, and that this is a worthy pursuit.

Me too. We're not identical, but we have similarities, and understanding them will likely allow us to better achieve mutual satisfaction.

This is my disappointment with Harris. He ran a fundamentally sound project into the ditch by claiming, entirely unscientifically, that his utilitarian ideal was the one word of moral truth - Thou shalt serve the well being of all conscious creatures - that is the whole of law!