Well, believe it or not, they
are voters and , more to the point, human beings who are subject to the same psychological biases and errors that you and I and everyone on this website are subject to - we can't help it, it's the way we are wired. When you "believe" something you will look for "facts" that support your belief or hypothesis, and disregard or rubbish "facts" that are contrary to your point of view. The principle of cognitive dissonance is alive and well and dwelling in all of us - the need to be consistent with our inner belief system. Festinger stated that to hold more than one view on a subject was to "flirt with absurdity" - we all believe we are good people and do the right thing, therefore we all rationalise our action to be consistent with that self image...
As a psychologist, I am more than aware of this phenomenon than most, but I still catch myself doing it at times...which scares the wotsit out of me.