I've heard it once described that the left and right wings are more like a circle. I'll use compass terminology to make it easier to picture.
at a starting point facing in (North), you can go left-wing or right-wing. At some point you hit the full definition. Left (East) and Right (West). However, after that, as you get more extreme (and become a wingnut), you start to lose that difference and eventually start to become the same (South).