I think you're onto something there with that comparison to survalist doomsday scenarios. Some people have very vivid imaginations and they fail to see how there theory is basically impossible and then when challenged they fall back to some trope about slippery slopes.
I think in some part it's actually a part of a bigger American cultural trope. We also have this unique obsessions with zombies and pandemics etc. etc. Kinda thinking I'm special, the rest of the riff raff die and I'm left alone to "make it" from a feral rock bottom.
My guess is it's American individualism and it's unique inflated sense of self worth (not to knock it =] it's got its plus sides!) + fascination with the biblical apocalypse. I'm not as familiar as I should be with the faiths of the founders of the colonies, maybe it's something that traces back to then?
