Simple. Prove that all those "scientists" that talk about having evidence for a RE are unbiased and are not influenced by the conspirators in governmental organizations. Prove that the fish-eye lenses are inadequate to discredit the videos. Prove that the light doesn't bend in such a way to provide the illusion of a round earth. Show us that the Ice wall doesn't work the way that it does, and that the guards patrolling it aren't there in reality. In short, disprove the FE. Of course, you can't do any of that.
You can take this and turn it round.
Prove there is a global (for lack of a better word) conspiracy
Prove that light does bend by the orders of magnitude etc required
Prove the ice wall exists at all
Prove that gravity doesn't exist
Prove bigfoot does/doesn't exist (depending on your view)
It's not worth taking that road, you must be able to come up with something tangible, short of going into space.