One of my favorite John Calvin quotes is where he says the Word of God's was self-authenticating. It carries its authority with it. No doubt, atheists like Dawkins and Hitchens, point to the horribleness of the OT. Scholars point to the ancient parallels of ANE literature. All together such cries rise up "it is not the Word of God... it looks human." This is not argument against the Word of God, for Scripture tells us that human men were carried along by the Holy Spirit. We worship a God who can condescend and in this condescention he makes himself known by way of covenant. Yet, God is sovereign and transcendant so that he sees to it that the very words of Scripture are 'God-breathed.'
So if God breathes out his what would be expect it to look like?
(1) Human beings are the ones who put pen to paper. Scripture did not drop from the sky. We are told:
2 Peter 1:21 For no prophecy was ever produced by the will of man, but men spoke from God as they were carried along by the Holy Spirit.Indeed God uses men in such a way that they write exactly what He has breathed out. Yet this is no theory of mere dictation. "Men spoke" but also "men spoke from God" and were "carried along by the Holy Spirit."
I do not, with good reasons we cannot elaborate here, subscribe to the theory that because men were involved in the process that the Bible contains errors. This is not to minimize difficulties but to affirm that at the end of the day God does not lie or mislead. If he is the ultimate authority behind the text, we should expect it, based on his character, to be error free.
(2) But if one means, as in the case of Dawkins, Hitchens, et al, that the Bible is immoral. But by this question you are forced to ask: who defines immorality? I believe in that this is one area where Doug Wilson sought to nail Hitchens, the reader may judge if he was successful or not.
If one wants to use an outside authority to seek to validate or invalidate Scripture, one is making no less a perilous move than that one accuses of his opponent. No matter how much reason or philosophy one uses at the end of the day you rely on it to be 'self-authenticating'.
At the end of the day it comes to issues of trust and submission. Do I submit to God and His Word or do I submit to myself. This is not to bypass evidence, persuasion and a right use of Christian reason to defend God's Word and convince others. We just have to acknowledge where the impasse always ends and that is at a fork in the road: I either go left on the narrow road where I bend my knee, or I go right onto the wide road of the stubborn heart.