Robertson's point is actually quite relevant for religious folk. When I was still a serious Christian, I too wondered how a purely secular approach to morality could avoid degenerating into relativism or a "might makes right" free-for-all.
Any arbitrariness in one's approach to morality risks relativism, as someone else can take a different approach and so reach a different conclusion. For example, utilitarianism becomes a much different beast if I introduce a caste system wherein I take a weighted sum of people's utilities. I may decide that one group's happiness is worth more than that of a different group.
Cheating is another issue that bothered me. If you can lie, cheat, steal, and kill your way to a good life and avoid all the negative consequences, then why not do it? This is the perspective of someone who does not value other people's happiness and only follows the rules because of the punishments for breaking them.
Contrast with a supreme judge. He's the source of morality, so there's no relativism. He's omniscient, so there's no getting away with doing something in secret. He's almighty, so there's no way to use one's might to avoid consequences. Is it any wonder that the devout can feel underwhelmed by secular morality? They can accept that atheists can be just and honorable, and that some are more righteous than most religious folk. What they have trouble accepting is that those moral precepts have a solid foundation without God.
Cheating and lying does not always devalue other people's happiness though. Cheating on the GRE doesn't obviously hurt other people. Lying (or misdirection) sometimes spares someone a painful truth or leaves them none the wiser. Like when a kid lies to his dad about where he was earlier this afternoon. These pretty simple counter-examples don't refute your point fully. I propose them because I think there is something lacking to say the only reason we can't cheat and lie our way to the good life is because it hurts other people's happiness. Sometimes it do...
Link to Blog Post: "Extremism in Thought Experiments is No Vice"
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This is a LW discussion post for Yvain's blog posts at Slate Star Codex, as per tog's suggestion:
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