This sort of concept highlights how just getting through can be a battle, especially if we fall back on quoting a book the other person doesn't even accept as having any relevance to them.
How can someone have sin, unless they have sinned against someone or something? We can talk about things like an occasional drifting over the speed limit but to then argue that such an event qualifies someone for hellfire does little to establish credibility. Refusing to believe something exists doesn't mean we don't have it - I'm not sure how many medics would offer denial as an effective form of treatment for any condition - but it does highlight how the first step has to be to break through the denial.
Salvation is meaningless if someone doesn't see any need to be saved. If you don't believe that hell exists, why would you need to be saved from it? If you don't believe that heaven exists, what value is the chance to spend eternity there? If you believe you get your time on earth and then become worm food, what does it matter what other people believe happens after you're gone?
That's the part where people sometimes like to play Pascal's Wager, but even that doesn't work because the most it can achieve is to argue that maybe people should believe in a god. When presenting with conflicting claims of Christianity, Hinduism, Islam, Judaism, Sikhism, Buddhism, not to mention a host of other smaller religions, Pascal's Wager falls flat because it offers no guidance other than to try and appease them all. And yet just comparing the three Abrahamic religions indicates that appeasing them all is impossible - how can one accept the claims of Christianity and Islam and combine them? Either Jesus is divine or he isn't - if he is then Muslims are wrong and if he is not then Christians are wrong - how can anyone appease both? And of course if it turns out the Hare Krishnas were right all along then we're all hosed. Well, except the guys in bright orange jump suits and funny haircuts.
