It’s what one researcher calls the “I Know I’m Right” syndrome:
Facts don’t necessarily have the power to change our minds. In fact, quite the opposite. In a series of studies in 2005 and 2006, researchers at the University of Michigan found that when misinformed people, particularly political partisans, were exposed to corrected facts in news stories, they rarely changed their minds. In fact, they often became even more strongly set in their beliefs. Facts, they found, were not curing misinformation. Like an underpowered antibiotic, facts could actually make misinformation even stronger.
In another study:
More than 1,000 Illinois residents were asked questions about welfare — the percentage of the federal budget spent on welfare, the number of people enrolled in the program, the percentage of enrollees who are black, and the average payout. More than half indicated that they were confident that their answers were correct — but in fact only 3 percent of the people got more than half of the questions right. Perhaps more disturbingly, the ones who were the most confident they were right were by and large the ones who knew the least about the topic. (Most of these participants expressed views that suggested a strong antiwelfare bias.)
Studies by other researchers have observed similar phenomena when addressing education, health care reform, immigration, affirmative action, gun control, and other issues that tend to attract strong partisan opinion.