But if the Atheist is wrong, he ends up in hell and the Christian goes to heaven he believes in, because he lived the life he preached. So who loses here? Obviously the Atheist loses, not the Christian, in both cases. So the more dangerous belief is Atheism. Are you willing to take this risk?
This is a great statement and argument if you will, but we would like to expand that a bit to other aspects of Christianity as follows for your pondering: If some are correct and a Christian can't lose their Salvation, then the person who believes this doctrine only, and those who believe a Christian can lose it by defecting from the faith lose nothing. They both gain eternal life in heaven because they both believed and lived the essentials of the faith. BUT if one is wrong and you can lose it as many scriptures proclaim, then those who are telling people they can be eternally secure even in their unrepentant sin, lose big time.
In fact the person loses even more because scripture says it would be better to have never heard the truth and believed it than to have heard it, believed it, then turned away from it. 2 Peter 2:21 proclaims this. So what is the more dangerous teaching? To turn a blind eye to some doctrine, but not uphold all of it, can be very dangerous for some. To only embrace rewards, but not heed warnings to what happens to those who fall away will damn many, as they look to excuse their unrepentant sin.
Another sad teaching that some adhere to is the diminishment of the spiritual gifts such as healing, tongues and prophesy since Jesus day. Some believe as their leaders do, that these gifts are not for today. They also go as far as to call the people who do believe in them, Satanic or crazy.
But if they are wrong who loses? If you don't believe in healing, then you don't even have a chance of being healed. If you don't believe tongues, prophesy and praying in the spirit are valid teachings for today, than you lose out, not the person who is believing AND experiencing the faith benefits of these teachings.
Also, if the Altar call isn't a work of the devil as some say it is, and then they don't allow it in their churches, they again lose. They lose out on possible church growth and health themselves and they lose out for calling other Christians manipulative etc. This is covered under Matthew 24:49, where Jesus says the beating of fellow servants of Christ, will not go unpunished when he returns, in fact many will be left behind to see if they can get it right through the big test of the last seven years.
And lastly, even though you can take this thought process to other church doctrine as well, the subject of the soon to occur Rapture of the church should also be looked at from this same angle. If the mid or post tribulation Rapture crowd are wrong and there is in fact a pre-tribulation Rapture who loses? Certainly not the pre-tribbers, but instead the mid and post crowd, some of whom are known for their vitriolic attacks on the pre-tribulation doctrine and people. If they are wrong, many of them who have become scoffers themselves will be left behind. But if the pre-tribbers are wrong, do they lose? No not at all, they just join the ranks of all the others who will all have to endure to the end to gain their Salvation.
What we must realize in all theses positions and doctrine is, the beliefs that take the most faith to believe in, all come with the most benefits to those who believe them. To those who believe in things they can't see, or perhaps even fully comprehend, go all the rewards that maximum faith affords them. To those who don't believe in the many maximum faith positions, they will reap what they have sown. Since little to nothing was sown or believed, this is what they will reap. What will you believe in? All, some, or none of the truth?