From what I think you're asking (correct me if I'm wrong), is that "right" and "left" in our political climate are interchangeable with conservative and liberal (respectively). We know that the more liberal something is, the more equality there is. This is why communism (which teaches that all men are equal) is leftist, whereas monarchism (which teaches that one family is above all others) is rightist. Changing terms don't really change for extreme points, but rather the center. It would take centuries for the political spectrum to shift so that the extreme left becomes moderate (i.e. Enlightenment).