I haven't looked deeply into his "outsider test," but it sounds like something Wittgenstein would have enjoyed: it presupposes some significant unknowns about how beliefs are formed--including atheistic beliefs. It's true that your parents believing something is the best predictor of your believing something, so if you equate "insider" with "raised in this belief," it clearly plays an important role.... calling every Christian 'deluded' smacks of petulance and whining at the fact that his Outsider Test hasn't resulted in every Christian deconverting and thanking him for delivering them from obscurantist bondage.
But what exactly disposes a person to convert from anything to anything? Loftus is apparently presupposing that conversion to atheism always results from a coldly rational disposition to follow the evidence wherever it leads--but if that we the case, we wouldn't have phenomena like Bedson, who deconverts and then spends his life begging and pleading for his former associates to validate his deconversion by joining him. It wouldn't fully account for Dawkins, or Coyne, or their type, either: even if their atheism were purely rational, that wouldn't explain their evangelism. What prompts them (even assuming they're right) to take on the doomed cause of fighting ignorance and error? What makes them want to spread their views, instead of being content with their own rationality?
Without some sort of answer to those questions, it's unclear whether the "outsider test" has any validity. Does "thinking like an outsider" make you objective? Or is it yet another brainwashing technique: given our facility for post-hoc rationalization, does "thinking like an outsider" actually set up the right conditions for talking ourselves out of belief--not because the evidence is good or bad, but because "pretending not to believe" activates the mechanism we have for justifying prior decisions? The latter is actually more plausible to me.
As an aside, I've noted the phenomenon that movie actors who play lovers, sooner or later end up dating. The stars of Twilight are a recent example. It might be nothing more than sexual libertinism and a tendency to casually form shallow relationships. But I've suspected for decades that something else is at work. I suspect that pretending to be in love triggers the manufacture of justifications for being in love, which in turn convince them that they really are in love. As a teenager I would have said "actors are so stupid, they fall for their own acting!" My original explanation wasn't very precise or nuanced, but it's substantially the same as the explanation I'd give today.
As another aside, I read something 20-30 years ago about brain-washing in Japanese POW camps. The trick I remember was that they had essay contests, with cigarettes for prizes, and they freely awarded prizes to jingoist pro-American essays--but prisoners knew they could improve their chances if they found anything positive to say about the Japanese. So they waved the flag vigorously, but included things like, "That's not to say that the Japanese are evil plain and simple; many of them suffer the deluded belief that their cause is just." After the POWs were released, they were found to have noticeably less anti-Japanese ardor than their brethren who were never prisoners. Which IIRC, was the opposite of the expected outcome. POW camp is not fun; you'd expect them to come away more hate-filled than ever. But viewing the Japanese with "insider mind" changed their views.