Edit to add: If you’re interested in the concept of an evil God in the context of Christian beliefs I recommend reading “Answer to Job” by Carl Jung. He doesn’t exactly make the Christian God evil but ascribes moral failings to God and frames Jesus as the redemption of God instead of the redemption of man.
Socrates answered this. If morality is objective or has an objective basis then it is necessarily independent from any God or god’s.
https://en.wikipedia.org/wiki/Euthyphro_dilemma
Edit to add: If you’re interested in the concept of an evil God in the context of Christian beliefs I recommend reading “Answer to Job” by Carl Jung. He doesn’t exactly make the Christian God evil but ascribes moral failings to God and frames Jesus as the redemption of God instead of the redemption of man.