An interesting new article today at the Skeptic's Dictionary, explaining the backfire effect. Several recent papers have found that information contradicting people's initial beliefs can actually increase their acceptance of those beliefs. This is true in political contexts and in religious context. In one example, people given false information about a Supreme Court nominee (which played to their biases) wound up retaining their heightened negative views of the nominee after having the negative claims refuted.
Skeptic's Dictionary author Robert Carroll concludes:
The backfire effect should be distinguished from the continued influence effect, whereby one learns "facts" about an event that later turn out to be false or unfounded, but the discredited information continues to influence reasoning and understanding even after one has been corrected. The backfire and continued influence effects should be disheartening to those who think that the first step in arguing with those who base their beliefs on misinformation should be to get their opponents to see what the facts are. Correcting errors may be pointless when dealing with some people. Critical thinkers, one would hope, would want errors corrected. At the very least, getting the facts right might prevent some faulty inferences and prevent one from behaving in ways that could prove harmful. For example, getting the facts straight about tobacco and alcohol would be a first step in guidance toward reasonable actions regarding those substances. Johnson and Seifert have argued that providing a plausible causal alternative, rather than simply negating misinformation, mitigates the continued influence effect. They may be right for some beliefs, but I have not found that providing a causal alternative to astrologers, acupuncturists, homeopaths, parapsychologists, or defenders of applied kinesiology, for example, has had much effect on true believers. Political beliefs, religious beliefs, and woo-woo beliefs seem impenetrable to facts that contradict them. Changes in these beliefs seem more likely to occur outside of direct confrontation with opponents.
This is honestly part of why the "don't be a dick" concept rings true for me. Most lay people will forget the fine points made in a discussion within a week, but they will remember demeanor -- say, whether someone was highly abrasive or very patient -- for a much longer time.
Several years ago, a sophomore intelligent-design advocate happened to be spouting off near a group of my friends; after getting waved over, and (unfortunately succumbing to peer pressure to perform) I proceeded to tear him apart, point by point, right down to the validity of his religious morality. I've got four (admittedly sympathetic) witnesses who will attest that I won on every single point, and yet I happen to know via word-of-mouth that that guy is still doing the same blasted thing, intermittently preaching and teaching Sunday School at a local church. Did I help any onlookers learn something? Maybe; a few people were nearby, but I didn't really look to see how they responded. I sure didn't help the ID advocate learn anything.
I am rather certain that the backfire effect is magnified by the culture of martyrdom certain groups encourage. A certain level of pigheaded determination is necessary for any pursuit, but there's a significant difference between, say, the rigor necessary to complete a research plan in spite of disappointing initial results, and the air of expectant, bristly defensiveness a "true believer" constantly wears. Touch it, and they immediately dig in, roll out the concertina wire, and peek out of their little intellectual pillbox, ready to fire at anybody who doesn't instantly run up the white flag. The guy I approached couldn't even respond coherently by the time I was finished with him, but he never moved from that little bunker he'd constructed, ruined though it should have been. It was the last time I let myself go on "full offense" in a casual discussion. Sure, I earned a congratulatory backslap or two from my friends back then, but I didn't actually accomplish a damn thing. I may have even encouraged that guy to become a more determined enemy of rationality, though I'm neither petty nor proud enough to locate and sit in on one of his sessions to see if he's refined his spiel.