There is such a thing as natural theology, a theology that doesn't presume the truth of revealed scripture from any religious tradition. Socrates, Plato and Aristotle had interesting approximations (acknowledging that there are limits to what finite human beings can know about an infinite God) to a monotheistic concept of God that is as far above paganism as quantum physics is above Aristotle's concepts of motion, attraction, form and matter, etc.
In "Science can answer moral questions.", Sam Harris tries to argue that it is possible to develop a scientific approach to morality. His efforts are well worth study. Indeed, we can think of his efforts as a kind of nature-inspired (in the sense of knowledge derived from observation) law. This is almost, but not quite, the same thing as Catholic Natural Law theory. Natural Law Theory makes certain unavoidable assumptions about the relationship between an infinite God and the natural world. Catholic Natural Law Theory goes one step further and says that the Natural Law is written by God in the human heart. The essence of Natural Law is instinctive, we may say, in a morally healthy person.
Harris is advocating something closer to "natural morality" built on a loose concept of human flourishing. He has some important examples to consider in his talk. He even cites scripture with a question. Is that scripture passage he cites right? He says it's from Proverbs. He may have been citing Proverbs 13:24 - "He who spares the rod hates his son, but he who loves him is diligent to discipline him."
Contrast the wisdom of this passage with the wisdom of St. John Bosco. Contrast it, too, with the patience of God! God doesn't immediately zap us! He lets us learn the natural consequences of our foolish behavior, first. Then, if we continue on a downward path, and especially if our lives have a deeply negative impact on others, he eventually calls an end to our mischief. The fact that he allows a lot of mischief to occur before he intervenes leads us to ask why God permits bad things to happen to good people.
Even when we are depending on God's inspired word for answers, we can't say that we have all of our questions answered!
God intends us to ask questions, especially deep, probing questions. He gives us tools to answer those questions, tools that include science, logic, scripture, tradition and moral authority. God invented all of these sources. It stands to reason (as St. Thomas Aquinas and St. John Paul II discovered) that they are ultimately compatible with each other, though it may take us a long time and much thought to recognize that compatibility.
Harris, it seems to me, runs into natural roadblocks to finding ultimate answers. It turns out (as one can see from a review of his Wikipedia entry that he, like many other scientists, does not believe in free will. He also has certain presuppositions about what human flourishing entails that a Catholic Natural Law philosopher would take issue with. Nevertheless, he asks important questions and proposes important insights to help answer some of those questions. He also seems to acknowledge that his approach has significant limits.
At the same time, it seems clear enough that his approach debunks the axiom of moral and cultural relativism, that all systems of morality and all cultures have an equivalent claim to adherence. All of the great saints have been able to do the same, because their moral reflections did not stop with citing scriptural authority or tradition.
I could be wrong, but it appears he might be someone who can remain in a serious discussion without demonizing those he disagrees with.