I don't really think it counts, but I'm going to nominate religion, or rather, that earth is flat, because god said so. Seriously, so many Flat Earthers bringing religion into a scientific debate. More then half the time, It's not even relevant to the conversation, and they're just trying to snag an easy "victory".
But holly, don't even get me started about jroa and his signature. So what if Hitler believed in the Round Earth theory? Are you implying that if I believe it, I too have the chance of becoming a tyrant and committing mass genocide? Well sheesh, better convert to Flat Earth! I mean come on, It's such a petty signature and it shows how petty some people can get.