Unless critical thinking is first and foremost, Unless a "belief system" has built-in corrective measures as far as testing its own truthfulness, then is would be correct to assume it is wrong.
edit: of course these corrective measures would be biase to support the "belief system's" viewpoint.
I'm not sure how that relates to the discussion at hand, that of beliefs being determined by geography. My point was that this sort of argument (that of beliefs being determined by geography, as advanced in the graphic in the original post in this thread) is often raised against theists, but it really proves nothing. How we acquired a belief in no way relates to whether the belief is true or not. The same could be said of atheists and agnostics in this regard as of theists.
One might also wonder what "corrective measures" are in place to test the presupposition of materialistic naturalism that forms the basis of the atheist's belief, and whether such corrective measures (if they exist) might be biased in favor of that belief system's viewpoint. Ultimately, all belief systems - including atheism - are based on presuppositions that cannot be absolutely proven.