My training is very much in modern philosophy - I once tutored a 1st year Plato course but managed to avoid reading much Plato for it!Oh, is that where the argument was originally formulated? I must get and read a translation. I was about to point out why the assertion was dubious (at best), but only have the argument(s) second-hand.
In the Euthyphro the argument is framed in terms of piety - does behaviour become pious simply in virtue of being beloved by the gods, or do the gods love certain behaviour precisely because it is pious? I think it's fair to say that the mainstream view is that a good god is good because of his/her support and creation of good things - not that things become good simply in virtue of being loved by god.
Interpreting Hobbes moral theory is a cottage industry in itself, but the basic idea on this issue is that public standards of value arise only when prescribed by an effective authority, that God is an effective and universal authority, and therefore whatever standards God dictates are good, independently of their content. When set out like that, I'm assuming it's obvious why that is the minority view!
(There are further complications for those who deny straightforward objective metaphysics for value - but the best theories along those lines also regard it as important to be able to explain why "I value it because it's good" comes out true and "It's good because I value it" comes out false, even if in the underlying metaphysics of the theory value is an expression of preference. It turns out that this is a pretty big technical challenge in the philosophy of language; I think this is one of the reason why mainstream contemporary moral philosophy, at least in the English-speaking world, is objectivist.)
I was trying to make sense of the idea that L/C is "ethical" and G/E is "moral". In ordinary philosophical usage, "ethical" and "moral" can be synonyms, but when they're distinguished "morality" means "obligations owed to others" and "ethical" means "pertaining to living a good life". Obviously on this usage the moral is a fairly important component of the ethical, but whatever is left over of the ethical - which is what I was trying to map to L/C - would be those parts of a good life that don't pertain to obligations owed to others. What would that be? It would self-regarding actions that contribute to a good life - which is what I meant by "self-cultivation".I don't at all get the "Self Cultivation" angle early in this thread. How is a monk cultivating the self more than rogue, and how could cultivating the self (as opposed to the group) be lawful? Does "Self Cultivation" have some idiomatic meaning I am not aware of?
In D&D tradition, monks are the characters most concerned with self-cultivation - taking deliberate stock of their lives and beings and taking steps to make themselves better persons - though paladins are also in this group, and samurai as well.
I took this as some confirmation that my analysis, grounded in an attempt to make sense of Gygax's usage of "ethical" for L/C, makes some sense, because it explains why monks, samurai and paladins are lawful.
As I also explained, it doesn't get all of D&D tradition right, because druids - favouring nature over self-cultivation - come out as chaotic.