I think everyone who mentioned cognitive dissonance hit the nail on the head. People naturally seek to reinforce what they already believe. Presumably, this served some evolutionary purpose at some point, but these days it just results in stubbornness as we find out that the first things people believe are often wrong. It's much more comfortable to try and change the world to fit how you view it than to change your worldview.
Another thought occurs. Many years of internets have trained me to suspect a troll in certain scenarios. I was driving today on a two-way street that I know well, and a guy yelled at me that it was one-way and I was going the wrong way. My immediate thought was that he was trolling me, even though he was probably just an idiot. What if they're all just trying to do a variation on this?
xkcd: SUV