In order to defend his moral argument, William Lane Craig advices his disciples to tell the sceptic, that everyone already believes in objective moral values:
In that sense, rather than get into an argument with someone over a premiss he already believes, it is better simply to ask him, “Do you believe (2)?” If he does, then the only point of contention is (1).
Read more: http://www.reasonablefaith.org/warrant- ... z2X82HJxiJ
Because this is said to be a properly basic belief. Craig also sometimes appeals to "intuitive knowledge" and "knowing deep down in our heart", which seems to be related to properly basic beliefs.
However the idea, that such beliefs are justified ("warrented") goes back to Alvin Plantinga, who proposes a religious reliabilism. After Plantinga we shall trust those beliefs, because they are created by god. And if they aren't created by god they become unrelaible (think about Evolutionary Argument against naturalism).
And this makes an appeal to properly basic beliefs, in order to make a case for theism, question begging. The theist presupposes god to lable some beliefs as "warrented".
Beside of being question begging I also think, that an appeal to the opponents belief is an ipse dixit fallacy. I have seem for example Craig often claiming, that Richard Dawkins beliefs in objective morality, because Dawkins said indirectly so (after Craig's interpretation).