We can leave the bible completely out of the argument.
There is an objective, external standard, there is a standard Giver, we violate that standard constantly, and will be held to account.
This is built into every human.
And the argument about things that are sanctioned in the biblical OT is an old and well-worn canard, but will continue to plague those who reject Who God is, because it will be impossible for them to fathom.
The "giver" is the collective society. The "objective, external standard" was created by a society. That is why, for example, slavery is sanctioned. It was considered normal and moral for the society of that time.