Why do people who don't believe the Bible try to use it as their weapon?

Why is it people who don’t believe in the Bible, that it is a book made by man and not the Word of God try to use the this so-called fake Bible to expose Christians has weak minded hypocrites? That to me makes about as much sense as someone who thought a text book say quantum physics was fake to refer to that book to disprove quantum physics. By using the Bible to try and prove their point are they not saying the book is real? I mean, they can’t seem to use independent text to disprove the Bible, and it would seem easy if they really had the goods.