Tom Woods1 has written a great article debunking the myth that anyone ever thought the Earth flat:
European monarchs’ initial hesitation to support Columbus’s proposed expedition had nothing to do with the idea that the world was flat and Columbus might fall off the edge. It was precisely the accuracy of their knowledge of the earth that made them skeptical: they correctly concluded that Columbus had drastically underestimated the size of the earth, and that therefore he and his men would starve to death before they made it to the Indies. (Thankfully for them, of course, the Americas, which no one knew about, fortuitously appeared in between.)
Uncritical acceptance of the myth was too tempting for many scholars, since it fit in so well with the caricature of Christianity they were already inclined to draw. "If Christians had for centuries insisted that the earth was flat against clear and available evidence," explains Russell, "they must be not only enemies of scientific truth, but contemptible and pitiful enemies."
Take that, Jacobins: happy Bastille Day!
1. Tom's most recent claim to fame is The Politically Incorrect Guide to American History, which on top of being a New York Times bestseller, was roundly denounced as dangerous by the Times's editors. (The Times wouldn't promote censorship, now would it?) If that's not enough recommendation for the book, please take my word that it's well worth reading. Even the most wary are surrounded by so many liberal lies that we can't help but believe at least some of them; this book is the red pill.
Jeffrey Burton Russell Inventing the Flat Earth: Columbus and Modern Historians (New York: Praeger, 1991).