He certainly expresses a belief in one. The reasons for that are ones that should be addressed, not evaded.
Given that many actual theists (Gardner being a pantheist, not a theist) claim a god as source for morality, then to claim that the debate over moral realism has nothing to do with debates over existence of gods is simply false.
God as a source of morality is irrelevant.
What would be the difference if
a. There is no god there are morals.
b. There is a god and there are no morals.
c. There is a concept of god and there are morals but the morals are not dependant upon a god.
d. There is a concept of god and morals are dependant upon the concept of god but there is no god.
e. There is a concept of god and morals are dependant upon god and there is a god.
f. There is a god and there are morals but they are not dependant upon god.
g. There is a god and there are morals and they are dependant upon god.
1.} a. , c. , f. there are morals regardless of whether there is a god and morals are dependant upon a god.
What tests would be used to determine if morals are dependant upon a god or the concept of a god. Just because some people, including pan and poly theists believe that morals depend upon god makes no difference. Just as there can be theists, pan theists and poly theists that don't believe morals are dependent upon god or the concept of god.
Therefore what difference would it make if there was a god or if there was a concept of god?
There is no way to say that any human concept is beyond science and observation. If so then people are just being vague as to what they are talking about.
I can generate a harm reduction model of morals based upon economic and social exchange. What value does god or the concept of god play in economic and social exchange that necessitates a belief in god or the concept of god?
What would be different in the system?
Science can only address ancillary issues of ethical questions; science cannot address central ethical questions themselves.
Oh jolly, that is a nice assertion of a personal belief isn't it?
If language can encompass the concept of morals then which aspects of morals do not resolve in terms that can be described in economic/social exchange terms and game theory?
What is so special about morals that they can not be observed?
If they can't be observed then they can't be defined. If they can't be defined then they are not even concepts.
You of course have utterly failed to address the central point that you simply cannot logically derive a "should" from an "is"; no matter how much evidence you collect, the ethical question and decision is still not a scientific one.
You have totally failed to demonstrate that, I would like to see your work. What makes you think that morals can not be observed and that they are not subject to science?
You can generate probability and cost benefit grids for the different choices and show that patterns will either have personal economic benefit, overall benefit and social exchange benefit.