MrRoboto -
There is literally no evidence for a flat Earth. We will leave aside the fact that we can see the Earth is a sphere (for the purposes of this discussion) and instead consider that no 'evidence' that is presented for there being a flat Earth accounts for all our observations from this planet.
The notion of a 'ball Earth' works with physical observations, the notion of a flat Earth would require a whole new set of physical explanations that explains not only ball shaped objects but flat objects also.
In our observable Universe objects over a certain mass are ball shaped; gravity causes this. We can measure the mass of the Earth and we know this exceeds the minimum required mass to cause it to become ball shaped.
Most flat Earthers also consider the Earth to be the centre of the Universe with everything orbiting us. That raises a whole new set of questions (such as how can galaxies move faster than the speed of light) as well as meaning the answers we already have (including verified predictions) no longer explain anything. Even maths stops working...apparently.
But as I said at the start, we can see the Earth is a sphere therefore all suggestions that the Earth is flat have to be based either in a profound ignorance or a profound sense of troll.