To the other posters,
I am convinced that Spherical's motivation for arguing this position are not “rational”. By this I mean that he (she?) does not believe the earth is flat because it is logically or scientifically consistent, or that there is any true evidence for it.
It may be that the person really does know the earth is spherical (thus his nick name) but is isolated and is using this concept as an excuse to interact with others on something that is not personally threatening.
Another significant possibility is that the person is delusional and truly believes what he/she is claiming. In this case it is impossible to reason with such a person. It may be the result of a mental illness or demonic deception. In either case, the person cannot “reasoned with” until the true cause of the problem is dealt with.
Another possibility is that the person is simply (demonically?) contentious and has confused emotional reasons for making outrageous comments.
In all of these cases, I doubt there is any productive reason for trying to reason with him about whether the earth is flat or spherical. Either, he can't accept the truth of the matter, or he already knows it and has other motivations for pretending to take that position.
I get the impression that many of the responders are actually trying to help Spherical reason through his position. I suggest that we waste no more time at this.
Perhaps we can identify what he really needs, such as true human emotional interaction and address that need. But in all cases, I suggest we pray for him (her?) because trying to reason with him in his own confusion is truly pointless as shown by his responses in this thread.
If he is sincere, only God can reach into his delusion and heal him. If he is not sincere, only God can reach into his heart and meet the need that shows up in this symptom of pretending to argue the earth is flat.