An underlying, pervasive belief in Dawkins's God Delusion is that science has disproved God. And, anyone who continues to believe in God is a wacko. Dawkins is especially outraged and perplexed at scientists like Francis Collins who are real scientists but believe in God.
McGrath, in The Dawkins Delusion, says "it's not that simple - and just about every natural scientist I have talked to about this issue knows that." (DD, 33) Stephen Jay Gould, e.g., acknowledged that science not only does not but, in principle, could not disprove the existence of God. But Dawkins, deeply ensconced in his hyper-naturalistic paradigm, write the following astonishing sentence: "I simply do not believe that Gould could possibly have meant much of what he wrote in Rocks of Ages." (In DD, 34)
Martin Rees is president of the Royal Society, which brings together Britain's leading scientists. In his book Our Cosmic Habitat Rees points out that some questions "lie beyond science." (In DD, 34)
The truth is, as McGrath points out, that the "great questions" of life cannot be scientifically proven or disproven. "Either we cannot answer them or we must answer them on grounds other than the sciences." Which means: the Dawkins assumption that science disproves the existence of God is essentially misguided.