Good points. As to other approaches to a governing ethic, the essential question is why should people should abide by that ethic. Most come down, in the end, to a belief in equality.

I share that belief, but I recognize that it is only something I happen to believe: it is of no consequence to anyone who does not share that belief. The same is true for all people regarding all beliefs.

I have sought an ethic for governing the governance of society that involves no beliefs, but instead follows from an observation within material existence that can be verified by every human being. It is this: no human being has any choice but to effect choices (that is, choose among perceived alternatives and take action to bring that choice to fruition).

That makes choosing integral to being human. We are all required to respect the capacity of other human beings to choose for themselves because to do so is to recognize them as fellow humans.

All of that is contained within material existence. To act otherwise is to assert by that action some status regarding the people involved that cannot be verified within material existence: a belief. No one can be required to accept some differentiated status based on a belief (without coercion or manipulation being involved).

Anyway, that's what I've come up with for an ethic.