The problem is that sacred texts like the Bible (other examples might be the Pali Cannon in Buddhism or Vedas and Upanishads in Hinduism) do not contain "flat contradictions". If people hundreds of years apart write down conflicting ideas that later get complied together by another person/group who are using those texts for non-logical spiritual guidance, in what way is that a meaningful contradiction? Also, the idea that wisdom must be strictly rational is a modern, scientific standard that these texts fundamentally disagree with.