Why do Christians think that it's Atheist who believed the world was flat?

Aristotle (about 350BC) noted the shape of the earth by observing its shadow on the face of the moon during a lunar eclipse. But the Christian church held firm in its belief that the earth was flat. Not only did they hold that it was flat, they judged as criminal all who held a different view. Almost 1500 years after Aristotle, they jailed Roger Bacon (1214-1294) for 10 years for his views about the spherical earth. The Catholic Encyclopedia of the period lists about Roger Bacon, "He was an author full of heresies and suspected views." The Christian church held the flat earth views into the 16th century AD and no one dared dispute it.