You are correct that they [governments] have all been as such [violent]. There is a "sleeper" factor here though, which indicates that this must not always be the case. This is childhood. Our society inherits its nature from that of the upbringing children receive. Currently, many people do not respond well to reasoned arguments from first principles, they have a mutant sense of entitlement, and we are violent. For those reasons, the government is violent.
It is not our nature which makes us aggressive; it is inherited through example. Early human society had different needs, a different perspective, and had not long been ‘above’ the animals. Examples of violence were omnipresent. I view violence as a chain; with rare exception, it it directly transferred from person to person.
So violence is the present state, but as we biologically are, today and right now, we can produce children who do not use violence if we simply do not teach it. As you would not expect a child to know Mandarin if you never spoke it in the home, so too violence will not be part of their vocabulary. Of course, this will not happen soon but abuse against children, and visible violence in the world has diminished, although it is still prevalent. My point is that we don’t have to wait for evolution of the brain, we are only waiting for social evolution.
An important point: once the personhood and sovereignty of a subgroup of people is recognized, it is hardly ever retracted. For instance, African Americans will never be slaves here again, and we won’t be taking the right to vote away from women. The minority today is in fact children; and theirs is the revolution that needs to be had.
(Part of this post is from a message I have previously written, so I apologize for the rubber-stamp aspect)
Please check out this video on this topic: http://youtu.be/NGjjFGJMujc