When I was in law school my younger brother started bombarding me with emails about how he was planning to fight parking ticket on the basis that he was sovereign individual and the locality that had ticketed him had no jurisdiction to do so. At first, I actually found responding to be a interesting--there are, after all, deep philosophical questions (as well as interesting practical question) about the bases for giving any particular governmental agency authority over a particular realm of human activity. The more I researched and responded, however, the more I realized that, though he had not done any of the type of research necessary to properly consider the issue at hand, he had already made his mind up about it and the actual answers I was providing held no sway. I started ignoring him--frustrated as I was with the seemingly pointless endeavor of engaging him--but eventually my frustration turned to curiosity. My brother is not a stupid person. How could it be that he could not only adopt such a ridiculous set of beliefs (a set of beliefs that were not only illogical and without bases, but which were also completely antithetical to enjoying and contributing to society), but also feel so strongly about them as to argue about them in spite of contrary evidence?
It's a question I still haven't fully answered, though my subsequent conversations and research into conspiracy theorists have given me a much deeper understanding of the phenomenon in general. I've mentioned before on this site that I was heavily influenced by Cass Sunstein (who was also fascinated by the subject for a variety of reasons and whose seminars I happened to be attending at the time), and I think the combination of his influence and my brother's trip down the rabbit hole fairly convinced me that the proliferation of unfounded conspiracy theories and similar ideas has a net negative effect on society. If those who know better allow such bunk to fester and be repeated with impunity, potential believers on the margins are liable to get sucked into the epistemologically crippling vortex of such thinking. While providing counterpoints to such bunk may have relatively little influence on those who are already true believers, every clear-thinking individual on the margins who is prevented from making the leap to becoming a true believer is a victory.