You do know that the rallies were in two different locations, right?
Of course. The view from the Washington Monument would be to the east for the Stewart rally and to the west for the Beck rally, and the base line of the two views, as presented, are about 3400 and 1400 feet from the foot of the Washington Monument, respectively.
With the Google Earth "3D building" feature, you can actually position your POV right at the peak of the WM. However, the view is very wide angle and its hard to identify the landmark buildings from there. To get views that look like the photos you have to slide forward along the line of sight.