Inaccurate "Religious" Beliefs About Secular Issues:
David Bernstein asks: "Why do people develop 'religious' beliefs about secular issues?" In this article, I provide an answer: Because, in most such cases, there is little incentive to learn the truth. The article focuses on political beliefs, where it is rational to be ignorant because there is so little chance that any individual vote will determine the outcome of an election. As a result, those citizens who do bother to acquire political information often do so for reasons other than the pursuit of truth. For example, they enjoy having their preexisting prejudices reinforced, "rooting" for their political "team" (much like sports fans enjoy rooting for the Red Sox or Yankees), or the like.
But the lesson applies more broadly. As I point in the article, polls show that large numbers of people hold irrational beliefs about nonpolitical subjects too. Thus, large numbers of people believe that we are being visited by UFOs piloted by extraterrestrial beings, believe in ghosts, and reject the theory of evolution. Wildly inaccurate beliefs about these subjects - like inaccurate political beliefs - don't harm most people in their daily lives, and they can be enjoyable and emotionally satisfying. It's fun to believe in UFOs or ghosts, emotionally satisfying to believe that God "specially created" you, and so on. Thus, for many people, it is perfectly rational to let considerations other than rigorous truth-seeking guide their belief-formation processes on many issues.
Unfortunately, individually rational behavior can often lead to collectively harmful results, as when flawed political beliefs lead to harmful government policies.
In an entirely different category are the relatively rare people who actually act on wildly inaccurate beliefs in ways that harm them personally. For example, Timothy McVeigh blew up the Oklahoma Federal Building because of his highly implausible belief that doing so would lead to the overthrow of the federal government by white racists, as depicted in the idiotic Turner Diaries. Obviously, McVeigh's actions instead led to stronger security measures, and to his own capture and execution. Such people are, however, very rare compared to the millions who hold foolish beliefs that do not directly harm them.
NOTE: I assume that, by "religious," David means something like "based on faith without any evidence," rather than based on belief in a God or gods. So defined, even atheists can (and often do) fall for foolish religion-like beliefs about secular matters.