I hope you'd agree, though, that the motivations are polar opposites. For me, that is enough difference. ;-)
Back in college in the 1980's (during the Central American mess) a history prof I greatly admired got into a discussion about Left/Right policies with another student. The student became incensed when the prof said, "The leftist guerilla is morally superior to the right wing guerilla." After some flame back and forth the prof finally said, "Yes, I agree that both types of guerillas are capable of horrific deeds. The distinguishing trait, however, that makes the leftist morally superior is that the leftist believes that by doing what he does everyone will be better off. The right winger, on the other hand, is motivated purely by self interest."
I buy that, I guess I always have. Maybe it was all that indoctrination at ages 9 and 10. Or maybe it's correct. :0)