Here is my argument, arranged point by point:
1) An atheist does not believe in a supernatural force outside of the universe that created moral laws.
2) If nothing made the laws, then the laws cannot exist
3) Therefore an atheist is speaking nonsense when he claims there are objective moral laws
OBJECTION 1: The laws are just there, and even if nobody made them it doesn’t mean they’re not there.
My reply: A moral law is not the same as the concept of thought or triangle. For it to be moral in any meaningful sense, it needs to impose some sort of obligation on me. But if nobody created the laws, nobody is imposing any obligation on me. It is absurd to say that I am obligated to the laws themselves, as they are not sentient. To say that I am obligated to others is also absurd, because that would be a moral law, and this circular.
To put it another way: To say that this moral law I discovered through logical deduction means I’m obligated to follow it still makes no sense, since there’s no reason I’m obligated to follow it.
Therefore, whatever I have discovered can’t be moral laws, and only seems like them to me.
OBJECTION 2: By saying that somebody would owe you an obligation, you are implicitly admitting a moral law, that is, in certain circumstances you would be obligated to do something. So your position is self-defeating.
MY REPLY: Not really. The idea of owing an obligation only makes sense if there’s a lawgiver. That’s my whole point. With no lawgiver, no obligation.
Thus, if an atheist wants to be honest with himself, he has to be a nihilist (of course, he has no obligation to be honest.)
So what’s off about this?
Malcolm the Cynic 
I think a tripping point here is ‘supernatural’. I agree with you that there’s no place for objective moral laws in a materialist universe – but I actually think Wright would agree there. I recall him being on record as saying that, though he was an atheist, he was never a materialist, which he always believed was absurd.
Wright may not call objective moral laws supernatural, but I’m also pretty sure he wouldn’t regard them as emergent or physical, which I think would typically leave only ‘supernatural’ for a lot of people.
As I said at more length on John’s site, why should anyone have to commit to some theory about where moral obligation comes from? You say it can only come from God; how do you know that?
For that matter, the extreme moral skeptic you posit can turn around and ask you, Why should I obey God’s laws? What gives Him the right to impose moral obligations on me?
That’s a very good question in and of itself. I’m starting to think that the key is eternal consequences, but I feel as if I’m getting tripped up somewhere.
The obligation comes from creator to the created being. This is in addition of obligation from the beloved soul to return love to the loving God
In retrospect, I probably should have restricted myself to one website. Oops.
In reality, I do think the moral skeptic can be answered, but a full answer needs quite a bit more than just creature–creator. To pick a pop culture example that’s ready to hand, in Avengers 2 the Vision doesn’t have a moral duty to obey Ultron or adopt his purposes.
Why is creator and created not enough? Do you think that fathers do not have obligations to sons, and sons to fathers? Is part of that obedience?
If not, then why does a much more powerful, more loving, and the ultimate creator not deserve obedience? A being who set our souls aside at the beginning of time certainly deserves obedience solely based on creation of the soul.
Lucky for us, he also is supreme love, and the ultimate example of all that is good. For we humans are weak, and could not obey and serve otherwise.
Sounds like the whole “if a tree falls in the woods…” riddle. In that, the answer is yes, because sound waves would still be produced.
Likewise in these we can ask: “If man were not around, would ___ exist?” Gravity? Yes. Space/time? Yes. Triangles? Murkier but I would say that that and other math, would exist even if man wasn’t around. Moral law?
I’d say it’s pretty clearly no, but perhaps wiser men than me can say why it would be*. But it seems to me that if we go by the assumption that billions of years passed before sapience arose, then it would logically be that there were no moral laws until sapient beings existed.
Though the idea of the heavenly bodies having a moral code is… a neat possible sci-fi story, it would have to entail them being sapient. Otherwise the moon would have to be charged with attempted murder of the earth.
*Yes obviously if there is a Divine, high-order being then moral laws would exist – if anything they might be more real than even the laws of math and logic. But we’re not talking about whether a Divine is around or not, we’re talking about a strictly atheistic universe.
To begin: morality is interpersonal and relational (*) —
Morality is interpersonal — Moral obligations and expectations exist only between persons. No rock owes moral obligations to, nor has moral expectations of, another rock. Likewise, no person owes moral obligations to, nor has moral expectations of, a rock (or a painting, say, Mona Lisa).
Morality is relational — Moral obligations and expectations exist only between persons having some relationship, and the relationship determines the obligations and expectations. A son has a different set of obligations and expectations with respect to his father than the father has with respect to the son, and both have again different sets of obligations and expectations with respect to a father or son of a different family. One’s set of moral obligations and expectations toward one’s neighbor is vastly different from one’s set of moral obligations and expectations toward some total stranger on the other side of the world. One’s set of moral obligations and expectations toward one’s countrymen is vastly different from the set of moral obligations and expectations toward citizens or subjects of a different polity.
But: morality must also be transcendent —
If moral obligations and expectations really are binding on us, whether or not we wish to agree that they are — that is, if they really are real — then they must be not only interpersonal and relational, but also transcendent; they must exist independently of, and logically prior to, us, individually and collectively. Moral obligations and expectations exist only if there are persons — plural. But, these persons in whose existence the reality of moral obligations and expectations is grounded cannot be us, for we are contingent beings. To try to ground moral obligations and expectations in our existence, or in our natures, just ends up denying that they really are binding on us, whether or not we wish to agree that they are.
Morality, to be *real*, can be grounded only in a God who is real … and moreover, only in a God who is a plurality of Persons
(*) Incidentally, understanding this point helps in understanding why it is that “liberalism” so consistently gets moral issues ass-backwards: “liberalism” essentially denies these two bedrock characteristics of morality. In fact, it’s worse than that, for “liberalism” implicitly asserts not just the denial of these characteristics, but the veryopposite of them. This is why, under “liberalism”, any action that the United States of America undertakes which furthers the interests of America is “immoral”, but any action detrimental to our interests is “moral”. This is why, under “liberalism”, opposing “liberal” soak-the-rich taxation (which, of course, is never meant to soak rich “liberals”) is “greedy”, since one may onself also realize a slight lifting of the tax burden, but cheering on the imposition of ruinous taxation upon others, even as one seeks to shelter oneself from the taxes and even if the spending based on that taxation accrues to one’s own class (or oneself, directly), is “moral” and “patriotic”, so long as the taxation and spending is contrary to the long-term interests of the nation and one frames it in terms of “the poor” or “the children”.
Bryan Caplan, a libertarian economist who blogs on EconLog is the only self-identifying materialist I know of that claims to believe in objective moral order. But how he grounds this moral order, I do not know since he does not go beyond the assertion that moral order exists.
Wright denies Nietzche and Dosteovesky. His attempt to derive Golden Rulevia pure logic is transperently silly and I do not think he answered the Nietzche-type objections that people have raised there.