Well I can empathise with the flatties because I do actually walk on a flat earth. I never seem to notice it being round and going upside down when I walk round it. Maybe that’s what they are on about.
Still, it’s not worth arguing about because of a belief. It’s when they start to make models and create systems out of it to base their beliefs on, that’s where they are gonna lead us into trouble. Then they may start to fill in the gaps with their own hypothesis and lead people down a never ending rabbit hole of confusion. And God help us if they ever get to that point.
They could even stop the younger generations in the future from actually progressing in anything because they will be stuck in a theory they believe without proof.
Here is Carl Sagan giving us an easy way of understanding. I hope this will help you flat earth folk before you get stuck down a rabbit hole