If you can't stand reality-denying fanatics, avoid /sci/
Flat earthers, all-of-physics-is-wrong-and-the-Establishment-refuses-to-recognize-my-genius, and you-can't-prove-my-perpetual-motion-machine-won't work are rife there.
Maybe some were trolls but many actually seemed sincere about their BS.
I shed no tears when the guy in the steam-powered rocket crashed and burned. "Think of it as Evolution in Action"