You may be right about that. I need to think about it more.
I think the entire talk hinges upon this connection he makes: "Values are a certain kind of fact. They are facts about the well-being of conscious creatures." If you accept that the purpose of values is to enhance well-being, then you can evaluate which values lead to the greatest well-being. Notice that he does not say that science can give us values. He says that it can answer moral questions.
For example, there is a lot of research showing, unanimously, that a materialistic orientation is a train wreck in terms of emotional and social well-being. Conversely, I have not seen a single research study suggesting that materialism is good or even neutral for a person. So that would be the kind pf research Harris refers to in saying that it can help answer moral questions.
I am both fascinated by and skeptical of research, since it has both strengths and shortcomings. I personally don't need a study to tell me not to be materialistic. My firsthand experience with values like compassion, kindness, patience, mindfulness, generosity, equanimity, etc. is all I will ever need to continue practicing and developing them further. However, I find that having some quantitative data allows one to speak a little more objectively about it, like "See? We're not just making this up." It's easy for people to write off certain values as individual preferences.
Buddhism wisely advises people to take a close look and see for oneself whether practicing something like selfishness or generosity leads to greater well-being. However, if the person never takes a good look, they may continue for years, decades, or a lifetime without even considering a change. Having research to support the importance of a value makes it a little less easy to dismiss. In my experience, it makes a good teaching tool, a way to get a foot in the door, to persuade someone to make the initial effort to practice something enough to get over the hump and to the point where they start noticing the effects. In the same way, I find movies like The Dhamma Brothers to be very persuasive.
My understanding of Harris's point is that scientific methods can be used as a litmus test, a reality check, on which values lead to the greatest well-being. Even though that approach is fraught with it's own potential pitfalls, it allows an approach that is a little less subject to individual biases.
What do you think?