I've been thinking about that, and I came up with this theory that this is a fundamental difference between faith and science
when the argument presented by the person is more like a scientific theory, and available data contradicts it, the reaction is often of interest, to adjust the theory to best integrate the data
but when the argument is more like religious dogma, that the person identifies deeply with, when faced with a contradiction that threatens that identity, it triggers an "identity protection" reaction that amounts to negation, rejection, and ultimately retreat from the conversation
please bring counterpoints so that we can refine or correct the theory :-)