Why is bible literalism so important to YEC?

I will bring the little book, "What is happening in religious eduction today" back next time to get a more detailable response. But I believed I read this question in the first chapter between the lines. Some how by isolating "SUnday School" but not haveing seperation of church and state BECAUSE (this is my idea) of post-60s relevancy literally figurable is able to get even the most liberal understanding of faith that evolution is not across. That was a short cut and somewhat subjective but I will bring the book and provide more than two sentences from which you will be as free to up make your mind as I am to pick up the phone.