There seems to be a bit of confusion here over terms which has led to some posts arguing past each other.
We can come at morality from a descriptive perspective and ask questions such as, 'how do moral systems function?' and 'how do people come by their moral convictions?'
We can also approach morality from a proscriptive (or normative if you prefer) perspective and ask questions such as, 'what should one do in a particular situation?', 'what is the best moral system?' and 'Are there such things as objective moral standards?'
Here is a definition of morality from a descriptive perspective. I have taken it from Wiki as it is as good as any other:
In its "descriptive" sense, morality refers to personal or cultural values, codes of conduct or social mores that distinguish between right and wrong in the human society. Describing morality in this way is not making a claim about what is objectively right or wrong, but only referring to what is considered right or wrong by people.
Note that a descriptive definition of morality does not say what right and wrong actions are or what the ideal moral system should be.
If we accept this descriptive definition, then it may be useful to clearly state whether we are proposing a normative definition of morality, i.e. what we believe moral values should be. I have seen a few posts, on this forum and others, that refer to morality
is this or that system, that seem to conflate a descriptive perspective of what morality is, with a normative view of what it should be. This generally leads to confusion.
For example, it is interesting to discuss evolutionary bases for morality, but this kind of discussion is more of the descriptive type (how do people come to get moral values?). That people get their moral systems from a book, or by evolutionary processes, or by the powers of reason and empathy, does not in itself answer normative questions, such as the one posed here, 'Is God necessary for objective morality?'.
For me, the answer to the question is that objective morality does not exist, whether or not God exists. I do not agree with Craig that objective morality exists and is a reflection of facts about God's nature. I think that the Euthyphro dilemma roundly skewers this idea and Craig seems to duck this challenge. God is a mind and is therefore a subjective entity. It could be said that I abhor torture and that therefore my abhorrence of torture is an objective fact about my nature. It still remains my
subjective value that torture is wrong, however, and it is not objectively true that torture is wrong, simply because it is objectively true that I believe it is wrong. The same goes with God, no matter what rhetorical tricks Craig employs here.
On the other side of the argument, the attempt to suggest that there is an objective morality 'out there' somewhere, is no less coherent or convincing. For this to be true one would presumably have to suppose that there are certain moral facts that are objectively accessible to scientific investigation, or that statements such as, 'Hurting people is wrong', express propositions that are either true or false (and not just true for me or for you, or sometimes, or mostly, or in these situations and not others). I am not convinced that the arguments presented thus far in this thread have established either of these cases.