The truth is that there are hundreds of ways to prove round earth with bare eyes and basic maths. There is no way of proving flat earth (obviously because it is a wrong model)
Why do flatties believe the Earth is flat? Because it beleived to be so before and for so long? I'm asking this seriously.
They're religion is to basically distrust everything that is supposed to be conventional knowledge as a psyop that's keeping them from the soul freeing truth that the earth is flat.
Because they think everything the state / science / educational system says, is brainwashing. They just can't see that some things are in fact provable and proven. What can you do...