For scientists it shows that if you are in agreement with most of your colleagues, you will most likely be forgotten while history remembers some crank. For advocates of Intelligent Design theory it teaches that claiming your theory is correct is no substitute for backing it up with experiments and data (even if you are right). For aggressively self-confident people the lesson is that sometimes being persistent and believing in yourself will just get you into trouble. For Catholics it provides an example of why you shouldn't insult the Pope.
(HT: Justin Taylor)