Conspiracy theories represent a known glitch in human reasoning. The theories are of course occasionally true, but their truth is completely uncorrelated with the believers certainty. For some reason, sometimes when people think they've uncovered a lie, they raise confirmation bias to an art form. They cut context away from facts and arguments and assemble them into reassuring litanies. And over and over I've argued helplessly with smart people consumed by theories they were sure were irrefutable, theories that in the end proved complete fictions.
— xkcd: volume 0
by Randal Munroe