It's the true and final test of school. They lied to you when you were five or six and you don't actually graduated from science class until you decide to test things out for yourself and make your own conclusion. Round Earthers are the equivalent of the ultra religious people that believe anything and everything they're told as long as the speaker has the right title next to their name.

Butt seriously, it blows my mind how pissed off the flat earth troll makes people. I swear there's a deeply buried trigger in people's head that turns them into children again because that was literally the last time they've ever heard about flat earth.

Another good one is telling people (I'm American) that we were tricked into nationalism by making us stand and pledge allegiance to our flag every morning before they ever taught us what pledge or allegiance even meant. Almost got fired from my job for saying that because people got so pissed off and ready to fist fight.

Same reason religious people get so serious about arguments against religion. I think the younger you were when any belief, true or not, that you latched onto creates a more powerful response when challenged.