@LintRoll:
It's because self-proclaimed religious leaders use it as a source of evidence, interpreting the book as they see fit in order to convince other followers to do as they say.
Then when someone actually makes the effort of dispelling the rubbish spewed by these people(using religion's worst enemy, rational thought), the sceptics are condemned, shunned and ostracized till the point is deemed valid by a majority.
Now it's time to take the dastardly road of said "mere metaphorical content" followed by the stubborn excuse of "but it's still the word of god so we're right, we win, burn in hell, may peace be with you".