They are in fact vivid illustrations of a striking truth about human beings: however intelligent and knowledgeable we might be in other ways, many of us still believe the strangest things. You can find people who believe they were abducted by aliens, that the Holocaust never happened, and that cancer can be cured by positive thinking. A 2009 Harris Poll found that between one‑fifth and one‑quarter of Americans believe in reincarnation, astrology and the existence of witches. You name it, and there is probably someone out there who believes it.It's rare to find a person who belives that UFOs are kidnapping people who doesn't also believe, say, that the moon landings are faked, or worry about chemtrails. The linked post asks if there isn't a fundamental reason why these sorts of people think the way they do; if, in fact, some people are just bad thinkers.
(h/t to RobertaX)
