Published study: pointing out factual errors in people's beliefs may actually make them MORE likely to continue believing
In a 2010 study, Nyhan and Reifler asked people to read a fake newspaper article containing a real quotation of George W. Bush, in which the former president asserted that his tax cuts "helped increase revenues to the Treasury." In some versions of the article, this false claim was then debunked by economic evidence: A correction appended to the end of the article stated that in fact, the Bush tax cuts "were followed by an unprecedented three-year decline in nominal tax revenues, from $2 trillion in 2000 to $1.8 trillion in 2003." The study found that conservatives who read the correction were twice as likely to believe Bush's claim was true as were conservatives who did not read the correction.
Another notorious political falsehood is Sarah Palin's claim that Obamacare would create "death panels." To test whether they could undo the damage caused by this highly influential morsel of misinformation, Nyhan and his colleagues had study subjects read an article about the "death panels" claim, which in some cases ended with a factual correction explaining that "nonpartisan health care experts have concluded that Palin is wrong." Among survey respondents who were very pro-Palin and who had a high level of political knowledge, the correction actually made them more likely to wrongly embrace the false "death panels" theory.
Together, all of these studies support the theory of "motivated reasoning": The idea that our prior beliefs, commitments, and emotions drive our responses to new information, such that when we are faced with facts that deeply challenge these commitments, we fight back against them to defend our identities. So next time you feel the urge to argue back against some idiot on the internet…pause, take a deep breath, and realize not only that arguing might not do any good, but that in fact, it might very well backfire.
The bold part really rings true with me. I've been arguing politics online for a long time. I've come to the conclusion that people's political positions are 90% or more generated by nothing more than tribally identifying with one side. Of course no one thinks about themselves like that. We all think we're freethinkers who form our opinions independently based on a wide range of available objective sources. Furthermore I think this polarization is getting stronger and stronger every day with the advent of the Internet and endless sources of partisan news delivery.
I'm sure this happens on both sides. I have about half a dozen ultraliberal friends on my Facebook feed who think that Palestinians can do no wrong, and Israel can do no right. They also tend to be the same people who post about GMO and got super worked up about Trayvon Martin, like it was some seminal moment in history. Although I admit I don't know anyone stupid enough to be anti-vaccine. Or at least they don't admit it.
I think Carl Sagan can say it a lot better than me: