"My argument against God was that the universe seemed so cruel and unjust. But how had I got this idea of just and unjust? A man does not call a line crooked unless he has some idea of a straight line. What was I comparing this universe with when I called it unjust? If the whole show was bad and senseless from A to Z, so to speak, why did I, who was supposed to be part of the show, find myself in such violent reaction against it? A man feels wet when he falls into water, because man is not a water animal: a fish would not feel wet." -C.S. Lewis
Back when I was not a Christian, I often used the Bible to argue against God. How can you challenge the internal consistency of justice in the Bible, if you yourself have no grounds to claim that justice is an objective value at all?