The real danger, of course, is being utterly convinced Christianity is true when it is not.

The actions described by Lumifer are horrific precisely because they are balanced against a hypothetical benefit, not a certain one. If there is only an epsilon chance of Christianity being true, but the utility loss of eternal torment is infinite, should you take radical steps anyway?

In a nutshell, Lumifer's position is just hedging against Pascal's mugging, and IMHO any moral system that doesn't do so is not appropriate for use out here in the real world.