They aren't arbitrary and subjective because God is not an arbitrary and subjective being. God in the Abrahamic religions is all-knowing, all-powerful and, you know, the creator of everything. From these premises, it's reasonable to come to the conclusion that what He has to say matters in a more fundamental way than what anyone else does. If He designed the very plane of existence we exist on, then His will is its very organizing principle, and therefore can claim the status of a universal law.
How are gods laws not arbitrary when it is arbiter of the laws? That doesn't follow. There's no other overseer.
Well yeah, from a DCT perspective it's obviously impossible for human beings to assess God's actions morally. "God is good no matter what he does" is a really improper way to say it, though, because God isn't just acting randomly. God has a will which is eternal and unchanging in pursuit of His purposes, and which explains all of His actions. "No matter what he does" implies that God would just do anything, but no serious Christian believes that. God would only do certain specific things that accord with his will.
Which is what I argued. Whatever god determines is 'good', so there's nothing exceptional or praise worthy about what god choses to do. If it's constrained by an 'eternal and unchanging will' then if anything it's less equipped to situationally react than we are. Unless you think god has established morality which it is
now bound by which means it exists outside of god.
Good is what ought to be. Saying God is good is saying that God is the judge of what ought to be. You're perfectly in your right to find that definition unsatisfying (so do I, in case that wasn't clear), but it is a logically consistent and meaningful definition. Secular morality still has trouble coming up with one.
Is god 'good'?
Theistic morality is a form of subjectivism. Saying that morality is actually grounded in god’s nature and expressed in it's commands doesn’t avoid this problem. Whatever it was god’s nature to prefer would still be right by definition and still diminish the significance of moral terms. Hence god simply 'accords'. If it's nature were different, or the complete inverse; if it was omnimalevolent god would still be 'good'.