At the very core of traditional Judaism is the concept of bechira or choice. No miracle is so unambigious that it can't be explained away as secular. No miracle is so overwhelming that you have to accept it.Christian theologian, C.S. Lewis made a similar point in the book The Screwtape Letters when he spoke of why it is that God does not make it clearer that He exists and is involved with our lives.
You must have often wondered why [God] does not make more use of His power to be sensibly present to human souls in any degree He chooses and at any moment. But you now see that the Irresistible and the Indisputable are the two weapons which the very nature of His scheme forbids Him to use. Merely to over-ride a human will (as His felt presence in any but the faintest and most mitigated degree would certainly do) would be for Him useless. He cannot ravish. He can only woo.Christopher Hitchens will always have an easy time debating Jews or Christians since all he has to do is demand that his opponents prove that God exists. Yet, God has chosen to keep Himself veiled so as always to allow humans to choose whether or not to believe. Thus, Hitchens' fellow-debaters cannot prove the existence of God.
As the King James version of the bible puts it, "Faith is the substance of things hoped for, the evidence of things not seen" (Hebrews 11:1). If we could prove God, it would not be faith. It would not require faith to believe in God and would be purely a matter of logic. Those who debate Hitchens know that God will not over-ride our choice by proving His presence. Christopher Hitchens can go on demanding that God show Himself in a material manner, but God will not ravage Mr. Hitchens (or any of us) with His felt presence. Instead He woos us with the sense that, in the midst of all of the credible scientific explanations of the universe, credible scientific explanations of consciousness, and credible scientific explanations of life, there must be something more.