Focus on smaller propositions first. Why are people afraid of there being no caring god? Because then evil people can get away with it, good people don't get any reward, morality might not be "absolute," my prayers have been for nothing, I would have to sacrifice my culture, friends, and worldview, etc. Leave a line of retreat for these smaller problems. The larger problems will likely follow.

Also important, I think, is encouraging someone to focus on painful thoughts. Sometimes will accept a line of retreat without focusing on their belief's weak points, meaning they never bother taking the retreat. Or they'll only take it strategically, a la this discussion. Other times, people will focus on painful thoughts without having a line of retreat, which can be disastrous.