Harbour articulates what I have long felt: That revealed religions are cluttered with arbitrary and useless beliefs and information that people could just as easily live without. (For example, why should anyone rational care about the genealogies in the Bible full of unpronounceable names, like the conflicting ones given for Jesus in the gospels of Matthew and Luke?) His distinction between "Spartan meritocratic" and "Baroque monarchic" wordviews states exactly what is wrong with the whole premise behind a "revealed" religion, since it is undeniable that one's chances of hearing about it are a function of history and geography. Children learn about Jesus (or Krishna or Muhammad, for that matter) in the same way they learn about Harry Potter, which demonstrates that there is nothing in the natural world which implies the truth of these made-up stories.
The Spartan meritocratic worldview, by contrast, leads to discoveries that in principle anyone could make just from following his own inquiries into reality. Harbour points out that a mathematician in Japan came very close to discovering a key insight of the calculus at about the same time that Newton and Liebniz were working on it in Western Europe, even though the two societies might as well have existed on different planets in the late 17th Century. So it's not surprising that people in many different parts of the world have developed philosophical outlooks that sound somewhat like modern Secular Humanism, ranging from Confucianism in ancient China and certain philosophical schools in India all the way to Hellenistic Stoic and Epicurean philosophy. Secular Humanism, unlike revealed religion, has a better claim to the title "perennial wisdom" because it is implicit in a rational study of the world.
I was especially struck by Harbour's argument that theists' best shot at deriving a god from a parsimonious and plausible set of assumptions came and went with Descartes' philosophical program in the 17th Century. Descartes' argument for a god also implied a theory of physics that just happened to be falsified by Newton's spectacularly successful alternative model. Descartes' candidate for god therefore fell by the wayside along with his physics. If theists haven't been able to come up anything better in the last 350 years or so, maybe they should take the hint and give up on the god business.