I think this claim is just confusing descriptive and normative ethics. Probably the most common confusion about ethics there is.

True, descriptive ethics is almost entirely composed of various facts about human psychology and sociology, but no normative claim can be deduced from these facts alone.

My view of ethics is that it's basically just a (often vague) set of principles in our minds. Some of ethics is in our genes, some of it is cultural. Different cultures may have different ethical principles. Fundamentally, it's about feelings – something is good, because it feels good.