It still mazes me, if only slightly, that he even cares what theists think about the existence of God, nevermind the ramifications in an "imaginary realm".
Given that how theists thinks about God/hell tend to affect others to some extent, I don't see it as strange at all. In adition, if someone holds a possision you see as ilogical, you'd probably point it out yourself. Add that he sees religious belief as harmfull to society, and he has just as much motivation to point out what he sees as flaws with their belief as a believer in hell has to convert others.
Note: I'm only equating your motivation with that of a theist, Achilles, not the source of it.