The Moral Argument for God - Premise 2

William Lane Craig's Moral Argument for God's Existence (which I find persuasive) goes like this:

1. If God does not exist, then objective moral values do not exist.

2. Objective moral values exist.

3. Therefore, God exists.  (By modus tollens. See "The Indispensability of Theological Metaethical Foundations for Morality.")

What about premise 2 (P2)? Is it true?

An example of a non-moral objective truth is: Abraham Lincoln was the 16th president of the United States. This statement is true independently of our apprehension of it. And, as an objective truth, it is true for everyone.

Objective moral values are values that are true independently of our apprehension of them. 
Consider this example of an objective moral value. I recently read another horror story out of Isis. Isis men raped a crying mother in front of her own children, one of which was a baby. Then Isis beheaded the baby and placed it on the mother's lap. Call this Example Q. 

(Stories like this may be true. For corroborated examples see Stern and Berger, Isis: The State of Terror. For example: "On May 28, 2011, the corpse of a thirteen-year old child was delivered back to his family in the town of Daraa, where the protests began. The child’s genitalia had been removed, and his corpse was burned and riddled with gunshot wounds... Human Rights Watch and others have reported that Syrian security forces were using rape systematically to torture men, women, and children, some as young as twelve years old." Stern and Berger, 40-41)

For the purposes of our argument Q provides us with an example of an objective moral value: To do Q is morally wrong. This is a moral claim. Is this moral claim true? Note that if it is true, then it is objectively true, and thus true for everyone.

Craig defends P2 this way. He writes:

"My claim is that we are justified in believing P2 on the ground of our moral experience unless and until we have a defeater of that experience, just as we are justified in believing that there is a world of physical objects around us on the ground of our sense experience unless and until we have a defeater of that experience. 

Such a defeater would have to show not merely that our moral experience is fallible or defeasible but that it is utterly unreliable, that we may apprehend no objective moral values or duties whatsoever. 

Our moral experience is so powerful, however, that such a defeater would have to be incredibly powerful in order to overcome our experience, just as our sense experience is so powerful that a defeater of my belief in the world of physical objects I perceive would have to be incredibly powerful in order for me to believe that I have no good reason to think that I am not a brain in a vat of chemicals or a body lying in the Matrix. 

As [atheist philosopher] Louise Antony put it in our debate, any argument for moral scepticism will be based on premises which are less obvious than the existence of objective moral values and duties themselves, that is, than (2) itself." (Read more: http://www.reasonablefaith.org/are-we-justified-in-believing-in-objective-moral-values-and-duties#ixzz3t4q3RCZF)