Yes, this is exactly what I mean. I could be the most rational of people and still consistently hold the evil views I have described (for the sake of argument, of course!), because good and evil. You cannot "prove" that a moral axiom is correct or incorrect, nor can you assume that it will be self-evident to everyone else just because it appears so to you.
OK, but is that not true for any axiom of any theory?
Let us make a try. Would you accept the following axiom for moral obligation and permission:
Obligatory(p) implies permitted(p)
No? (it is one of the deontic axiom most people working theoretically on laws accept; obviously a society in which that principle is not respected make it possible for the power in place to put anyone in jail, by just making some service obligatory and also interdicted !)