I think the correct answer is that God, not we, decides what is right and what is wrong.
Well, yeah, I believe that was the answer I gave. Did you read something else into it?
How do we explain that genuine believers - indeed, right here on this little forum - may have such different ideas of what is right and wrong from God's perspective? Certainly, if there is a God then He is the sole arbiter of what is right and wrong, but how this translates into individual lives is a bit of a mystery. Why does "What I think God thinks is right" sometimes differ dramatically from "What you think God thinks is right" even in the lives of sincere believers? If the answer is "Oh, Believer A is being guided by the Holy Spirit and Believer B is not," who decides who is really being guided?
The most honest answer is probably: We each decide for ourselves what is right and what is wrong and hope we are being guided by the Holy Spirit. Or more cynically: We do what seems right to us and tell ourselves God surely agrees. Sure, in some situations we have specific decrees like the Ten Commandments to guide us, but in the vast majority of situations we make a determination for ourselves.
Consider the old question: Would murder become "right" tomorrow if God declared it so? Why does the God of the OT seem so repulsive to so many people - is there a "God morality" that is different from the "human morality "written on the hearts even of unbelievers? Do the commands of Leviticus strike you as "right" by any comprehensible standard? Why are books like
Is God a Moral Monster? (an entirely Christain book) necessary?
It appears you asked a one-line question to which you already had the answer and were anticipating the simplistic one-line responses you got. Here at The Church of What O'Darby Believes, we find Christianity too mysterious for one-liners.