Buuut, you can see Jupiter's moons orbiting with the most basic telescope, they wouldn't orbit a flat disc, nor would anything that far away have an inclination to face earth at all times for the illusion to hold.
So if Jupiter is round, and it has moons, and earth has a moon, we are flat?
I have a brain, my dog has a brain, I can play an intelligent game of chess... so by your logic my dog can too?
Function is not the same as composition.
A piece of metal can be used as a hammer, something to write on, or a dangerous weapon. Just because their function is different doesn't mean it isn't made of the same things with the same properties.
All we need to do is say that the Earth is made of the same things (atoms) as Jupiter and we can conclude that the same things that govern the Atoms on Earth govern the atoms on Jupiter.
That's not what he was saying, though, so what's the relevance? 
And obviously if Jupiter and Earth are both composed of atoms (not proven, by the way), they are governed by the same laws. Conditions at the time of their formation could have altered their shapes. I've always thought the Earth's direct contact with the Universal Accelerator could be the reason somehow that the Earth came out flat. Or, it could be its size itself. The flat Earth is much larger than anything else in the known universe so it would be naive to assume that it would form in the same way.
Conditions at the time of their creation DID alter their shapes(very slightly) and composition but they're both still bound by the same rules.
Still not sure how you figured the Earth is larger than anything else in the known universe. Jupiter's size dwarfs us. How do I know? Parallax measurements are a good one. That gives us distance. Then we take it's apparent size in the sky and use that and the distance to determine it's true size.
And while you are accurate in saying that we have not proven that Jupiter is made up of atoms, the simple fact that everything that's fallen from space is made up of atoms and we haven't found anything NOT made up of atoms (aside from Energy), then I don't think it's a leap of faith to say that everything solid appears to be made up of atoms.
Unless all the planets are nothing but holograms.