Nothing will ever shut these people up.
Wikipedia entry on "True Believers" outlines a similar syndrome in another area of belief. It is much like Bush Hatred Syndrome...you begin with the belief that Bush is evil, and then pile up "facts" to support what you believe. People may disprove individual facts, but to the "True Believer", there is always something formed in a "yeah, BUT"-tal that veers away and starts the cycle again. When faced with contradictory fact, a True Believer will just latch onto another set of facts, because the truth, that their basic supposition is flawed, cannot be examined.