Your axioms are underspecified. When you say [1], you really mean that human notions of good and evil change over time. Gods aren't affected by human notions, of course.

That's the thing with logic: your conclusions are only as good as your axioms. It is only a useful way of either verifying a line of argument, or of teaching an argument to somebody, or something like that: logic doesn't deal with truth, only provability.