(I only make this claim based on your challenge about asking everyone whether they believe that the Earth is round before saying that the majority believe it so.)
I challenged his claim because in many third world countries, many people are such horrid conditions, i seriously doubt they have considered the shape of the Earth, or have any clue why it should be a certain shape.
They have other things that they are thinking about, like, where their next meal is going to come from, or how not tot get shot be the local warlord. I seriously doubt many of these people have even considered the shape of the Earth, so to say the majority of the world thinks a certain way is ludicrous when part of the world doesn't even get the luxury to sit around and thing about such things.