Had an argument with a kook who believed that vaccines were bad for them, animal research did not benefit humanity or that organic food was somehow different than any other food?  You may have asked them if they believe the Earth is flat also.

Well, some people do believe that also.   Orlando Ferguson made the rounds in the late 19th century, reciting a 92-page lecture with his flat planet theory of geography - his last remaining map, painted with watercolor and which represents the Earth as a giant, rectangular slab with a dimpled upper surface was just donated to the Library of Congress.

Ingenious 'Flat Earth' Theory Revealed In Old Map By Natalie Wolchover, Life's Little Mysteries