It is my guess that there are no sailors, astronomers, or indeed any notable scientific thinkers among the ranks of the FES. So in essence, it is a "society" of ignoramuses who have fantasized for so long that they've begun to believe their fantasies. They've created conspiracies and convoluted explanations to defend their new-found views. Yet, by their own claim, will do no footwork to prove them or seek the truth otherwise.
If you lived on top of Mt. Everest, and looked out your window, you would see the curvature of earth... so enough with the "look out your window, what do you see", b.s.
If something isn't obvious, they'll state what is, and fabricate reasons for what isn't. They deny all knowledgeable claims made by credible sources that may threaten their reality. They'll use wishy-washy science-y-wienc-y (thank you Dr. Who) sounding theories, throw around conspiracy theories, answer with questions, and make excuses... all to stale-mate a debate and avoid having to give a good answer or admit being wrong.
They're probably all individuals who dislike, distrust, or are afraid of technological and scientific progress, including any manner of space exploration.
Willful Ignorance is their prerogative.
Amirite?
Either that, or they all actually know the earth is round, and we all be postin' in a TROLL FORUM SOCIETY.