It is hard even for an atheist to deny that the Bible is relevant to understanding the world around them. In order to understand history, culture, traditions, literature,government and legal systems it is foolish to deny the relevance of the Bible.
At the risk of being Clinton-esque, I suppose it depends on the what the definition of the word "relevant" is. Your point regarding the importance of the Bible in understanding Western civilization is well taken, and I agree with it completely. On the other hand, I can attest that as someone who is not a Christian that the Bible has virtually no relevance in my day to day life, any more so than any other book of scripture.