We consider hypothetical deities moral or immoral based on whether or not they agree with "arbitrary" rules like not hurting people unnecessarily, not the other way around.
Some religious traditions disagree. There are, in fact, people who believe God is by definition good and therefore any known commandment of God is good if we trust its divine status, because our own moral sense is fallible but God is not.
Link to Blog Post: "Extremism in Thought Experiments is No Vice"
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