I highly recommend Camus' "The Stranger" for a start
Hated the stranger with SUCH a passion. Worst book I EVER read.
Seriously, just because it has a message, doesn't mean yeu're allowed to butcher it with pathetic writing >.>
Horrible novel that uses "it's a work of hard lulz" as an excuse for its' mediocrity.
That being said, a much better, and more effective choice of books, would be Siddhartha.
If you need a god to find happiness, go for it. Some people need A/C while others can handle the weather just fine by themselves.
If you're going to bet that big, be certain. You may very well have an uncomfortable time explaining that comment to God one day.
This assumes god exists fully, and even then, the point still stands. People need to believe in SOMETHING in order to survive the insanity of life. It doesn't matter if they believe in god, themselves, their family, or a giant flying sock golem in outer space that shoots bananas out of its' ears.
So long as there is belief, there is hope. Once hope is completely gone, with nothing left to fall back on... then they are already dead, even if they're still technically breathing.
If there is a god worth worshiping, I'm sure they'll understand that someone had issues with the whole blind faith in nil for solid evidence, so long as that person tried to understand the best they could. There's literally THOUSANDS of religions, all of which claim to be "the one true god". Seriously, pick a random number between 1 and 10,000. If yeu pick the wrong one YEU BURN IN HELL FOREVER. I'd like to believe that there's a bit more to it than that, and that even athiests, if they did their best to understand the information provided to them, could not be expected to believe the unbelievable. Why create a being whose mind is more logical and requiring evidence and solid proof, then condemn them for those very same traits? Such is not the work of a god worthy of worship, but of an arrogant little brat of whom I would refuse to worship even if I had solid evidence for existence. I will not tolerate injustice simply because of a threat of retribution. If that were how god really worked, he can go to hell himself after he makes it.
However, I'd like to believe that this isn't how a being who is supposedly smarter than I am thinks. I'd be kind of sad if I were better than god himself. I don't think my ego could take that, it'd explode.
That being said, there may, or may not, come a day of explanation. If they understand why they said the comment, and can back it up, I don't think they'll go wrong. We can only base our decisions on the information given us, and the evidence presented. We can bicker over interpretation of the evidence we have, but it's just that... interpretation; personal in nature. Noone will ever interpret EVERYTHING right. That they at least attempted to, instead of blindly following whot they were told is likely going to be more important than those with blind faith who 'got it right' but for the wrong reasons.