Those who are serious about it fear that if they provide arguments, you'll rebut them.
Flat earthers (I've found, in my experience attempting to engage with them) refuse to even entertain a specific flat earth model. What I mean, there are several possible ways a flat earth might work. One way would be a static, non-moving earth. Another way would be a rotating earth. I've found that flat earthers refuse to even fucking pick one of those so that we can have a discussion about it!
Because there are experiments you might be able to do to tell the difference between them. But they fear that. So that don't want to pick one.
They also refuse to offer a way of determining where on the flat earth you actually are. Many of them don't realize that they are (that they must) refuse this, but they do. Why? Because if you had a map of a flat earth and a map of a globe earth, each of those make predictions about what portions of the earth are lit by the sun. With the globe earth, half the globe is lit at all times. With the flat earth, there's a circle that's lit.
You could collaborate with flat earthers you trust and travel to different parts of the world and you could say, "okay, flat earth predicts the sun circle shouldn't be here yet, but globe earth predicts I should be on the half of the earth that's lit" - there are lots of experiments you do like that, so flat earthers MUST refuse to provide a way of knowing where they are. Because that's their "out" - that's how they can say, "the elites tricked me! I thought I got on a plane and traveled to Rio but actually they flew me around in circles for a few hours and landed me some place else! That's why this experiment failed!"
