Well, first of all, there's no biblical way to justify not believing. This should be oblivious. The bible is the word of God if you believe. Naturally, it advises to believe.
If you don't believe, well, also naturally, those passages have no meaning for you. It's as simple as that, and that's why there will always be friction between theists and atheists.
As for my own reasons, well, for starters, read my story in the actual deconversion story topic Dawn. Even you don't agree, you might be able to understand why this damages your will to believe. Can you say what you do think of it? For me, I am highy pragmatic about people ''feeling'' God. It's subjective. And because I had such negative experiences with it, which turned out to be my own mind, I am not very inclined to give faith the advantage of doubt.
I've also got other arguments, but those are fairly untested and orginal. Plus, I am not good at debating, so I leave those out this topic.
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