Map projections take into account the curvature of the earth. If the earth were flat, we wouldn't need map projections at all.

Look at a Mercator map of the world. Note how the farther you get from the equator, the more distorted the sizes of the continents are. The Mercator projection is used for navigation, it is designed so that a straight line drawn between any two points on the earth will have an angle equal to the compass course a mariner would have to steer to travel between them. It also has straight, parallel and orthogonal latitude and longitude lines so that exact coordinates for any spot on the map can be quickly and easily determined without calculation, and rhumb line distances between locations accurately measured. The price you pay for this is that the latitude lines are not evenly spaced, and Greenland is bigger than Brazil.

But it is a good metaphor for a favorite point I'm trying to make here all the time. There is no "correct" map projection, just as there is no "correct" political or economic theory. You are entitled to pick and choose, or even devise your own tailored to your particular needs. If you want to plot a continuous compass course (rhumb line) between New York and Moscow, you use the Mercator projection. If you wish to plot the shortest possible (great circle) course between the two, you use a map based on the Gnomonic projection. Its not a question of which is right or wrong, but which is appropriate for your application.

The theories we use to interpret the world around us are just tools. We get to pick the ones that work best for our purposes; although not arbitrarily of course. But none of them is intrinsically correct. This is especially true in the behavioral and social sciences. This is why the strict ideological solution can get you into so much trouble if you insist on using it in every situation.

We need to constantly remind our Conservative friends of this, or they will surely sail right off the edge of the earth trying to pound history into an ideology that doesn't quite fit.