If the earth is a globe it would be impossible to accurately represent a sphere onto a flat surface.
But since the earth is flat is becomes extremely possible.
*wraps head around this one*
Let's simplify this FE argument!
1. Maps are very accurate since any normal person can use a map and verify that it works.
2. Maps are flat (that is, usually they are printed on paper)
3. One cannot accurately represent the surface of a sphere on a flat surface
4. Thus, since our maps are accurate, the Earth is flat!
But then of course when you navigate with a map in your day-to-day life you're usually working on a very small scale. So in that case flattening a spherical map doesn't lose much accuracy. And then you've got to remember that the Mercator map is widely accepted is being a gross misrepresentation of the Earth since, in keeping the latitudes perfectly straight (for navigation purposes), it blows the continents way out of proportion. That's why we have the Peters Map:

Or the one in sokarul's post.