The “True Believers” simply discard rationality. Logic no longer matters. They know with full conviction and absolutely zero doubt that they are right, regardless of any and all evidence to the contrary. There is unfortunately very little negotiation one can do with that mentality once a person in the grasp of it decides you’re an “agent of evil” - and that’s a comically easy line to cross.

Source: I’ve got a Christian Fundamentalist uncle, which is always… shall we say, interesting at family gatherings, especially considering that I was raised broadly similarly to him but am now staunchly atheist and he knows it.