Re: Question - please help me get this

A better question would be "Why does an atheist use the bible to disprove it if they don't believe in it anyway".

What does a challenger's belief or not in the Bible have to do with anything?

A challenger of the Bible uses the Bible to challenge the Bible because, if you want to study something to ascertain the truth or falsity of it, you don't do so by reading something else! And when the challenger rightly points out that the Bible itself contains quite a few inaccuracies, inconsistencies, and outright contradictions, without even considering the validity of the various stories themselves, Christians dismiss the challenges with pre-packaged explanations which exist outside of scripture, as if God's Word, if it were true, requires someone else to explain it. (Isn't that what the Catholics told people before the Protestants finally got fed up with what the Catholics were doing with Christianity? Pot, meet Kettle.)

If I told you one thing today, and something else tomorrow, you'd might consider me a liar. If I told a police investigator one story today, but varied in the details in a subsequent telling, they'd rightly assume that I'm lying to them and grill me further. That's how it should be, don't you think?

Christians believe that Matthew, Mark, Luke, and John are all different sources who have a different take on things, and certainly, any two normal, non-God-inspired people telling a story that's four decades old just might get a few of the details mixed up. But when Christians insist that the Bible is the de facto ultimate Truth, which is why we should believe in Jesus, shouldn't the stories in the Bible stand up to scrutiny just a little better than what we'd expect from witnesses to a vehicular crash during rush hour traffic?