In the same sense that "nutrition" is objective: there are multiple viewpoints that are equally valid (or at least similarly valid within a reasonable range), but there are also viewpoints that are clearly wrong.Oh? You believe that morality is objective?
Reasonable people can have diverging views about the nuances of nutrition (e.g. how many servings of vegetables per day is optimal) while still recognizing that a diet of rocks or arsenic is not nutritious. Likewise, reasonable people can have diverging views about the nuances of moral behaviour while still recognizing that genocide is immoral.
You only need to start with a few basic, widely-accepted premises to infer a pretty robust moral system, such as:
- The object of morality is the well-being of thinking beings
- In general, we find life preferable to death, the absence of pain preferable to pain, and happiness preferable to sadness, all else being equal.
From what I understand, Matt Dillahunty drew heavily from Sam Harris's arguments in The Moral Landscape, though I don't know if Dillahunty agrees with Harris on every point (and I personally haven't read the book).