^ also, an empathic person who cares for others, probably will hesitate to use his elbows, or to downright use force to eliminate another, even if this other one may be the pure evil.
I would say that the left as most of the people understand it, have shown no more mercy than right-wingers (speaking of Lenin and Stalin on the left and Hitler on the other) when it comes to mass slaughter and such.
However "the left" had at least some better scientific backup to justify their actions (revolution theories of Voltaire, Rousseau, or much later Marcuse. In this respect, any revolution had to be discussed, if the means to reach the goal for a better society, really justifies brute force and killing. If not, better let it go. It has not helped the ordinary man that much, though.)
Let me ask another question: Was Djinghis-Khan politically left, or right ?
