If no divine law is recognized above the law of the State, then the law of man has become absolute in men's eyes--there is then no logical barrier to totalitarianism.
Imagine a person who comes in here tonight and argues 'no air exists' but continues to breathe air while he argues. Now intellectually, atheists continue to breathe - they continue to use reason and draw scientific conclusions [which assumes an orderly universe], to make moral judgments [which assumes absolute values] - but the atheistic view of things would in theory make such 'breathing' impossible. They are breathing God's air all the time they are arguing against him.
It is important for the apologist who desires to be obedient to the Word of God in defending the faith to pay special attention to the fact that throughout Scripture, God's veracity is not defended, but accepted from the outset on His authority. Unless we have more wisdom than that contained in the revelation of God, we should take the same attitude.
We must not be satisfied to present Christianity as the most reliable position to hold among the competing options available. Rather, the Christian faith is the only reasonable outlook available to men.