Is the flat earth theory the nuttiest tinfoil hat theory ever?

[I spent the winter writing songs about getting better]

Not when there was a lack of proof against the theory. Believing in it now makes you a weirdo.

There's basically never been a lack of proof against it. As Al noted, virtually no one in Columbus' time believed the world was flat. The Ancient Greeks wrote about the world being a sphere, one noting how ships appear on the horizon itself being proof of that.