Personally, I joined because I saw some fairly obvious flaws in the theory when put to practice, and because I found it interesting that any and all direct evidence, such as photographs of the curvature of the Earth, reported distance traveled based on flight paths, and the like, are disregarded as conspiracy.
My honest belief is that, with the exception of a few conspiracy theorists, the forum is largely populated by people trolling others and getting a kick out of aggravating other faceless people. I occasionally check on here for a laugh, or to see what new "proof" one of the people claiming to believe in a flat Earth has "found," then chuckle to myself.
Personally, I don't see need to argue the fact of the Earth being a sphere any more than I need to argue the fact that I have a table in front of me; I have personally seen and verified the evidence and witnessed the fact of it. I just stop by here to see if I can stump a troll once in a while. So far, I haven't been disappointed; they always fall to saying, "Conspiracy! False facts! You can prove nothing!" with no backup to it.
Thanks, Flat Earth Society, for keeping me amused.
