One of the difficulties in considering ethical theories is their apparent dependency on metaphysics. It would seem that in order to do good you have to understand what good is and what makes something good. This can be frustrating, as metaphysical considerations are at least as contentious as moral considerations. Bringing metaphysics into a conversation reduces the chances for reason to prevail.
For example, human rights cannot derive from a supernatural source if there are no supernatural phenomena. Disallowing supernatural explanations of government is no loss if the "divine right of the king" is historically as likely an outcome as "inalienable rights endowed by our creator."
Fortunately, there is a way to get rid of metaphysical baggage, even allowing for supernatural explanations. Since supernatural phenomena cannot be observed (if they could they would be natural phenomena), then their meaning must stem either from the force of authority or from mutual consensus. All possible ethical theories, supernatural or otherwise, ultimately boil down to these options. This is because morality is never strictly a personal matter. Morality is always an understanding between people who may have different individual perceptions. I can't unilaterally decide how the people around me will be treated unless I'm prepared to back that up with force. Even if we agree that right behavior is defined by the divine, the operative force behind that definition is WE AGREE.
There are only two possible fundamental ethical theories:
- Might Makes Right
- Mutual Consent
All other options are simply derived from one of these. The way you get at the root is to ask the question: According to Who? Utilitarianism? Whose definition of utility? Natural law? According to who? Divine right? According to who?
Your moral opinions, then, depend upon which of these options you find preferable. For me, the choice is perfectly clear.