Because a scientist can generally detach themself, they aren't emotional about maintaining something more than they are prepared to challenge it. And to answer, the rationality of the theist scrutiny (without challenging the belief itself) is done so from within the same frame of reference as that which is in support of that belief. Therefore the belief itself was never trully challenged regardless of how honest that theist believed their scrutiny to be.
Coming soon: Banner image-link to new anti-islam forum.