If you think that governments are some sort of special organization, and that the same problems would not occur with any other power, you sir are a fool.
Haven't seen that yet, mostly due to free market influences. (There is a good reason why your neighborhood store owner is not also a flagrant lawbreaker -- it's bad for business)
But substitute "armed gangs", "the mob", "terrorist organizations", etc -- works great.
That law that the store owner doesn't dare break is what holds him back!
Not trying to argue, but it's a non-sequitur.
The industrial revolution had corporations over-taxing the body politic. It was the natural result of taking rural agricultural ethics and putting them in a mechanistic world. It led to labor reforms. trust-busting, and labor unions. Sucked a lot, and lots of folks probably died early, but it was hardly the stuff of the holocaust. You have to remember that everybody was just figuring all this stuff out as it was happening. Once it became clear where we were headed (and that we didn't want to go there) then the government, which defines corporations, defined what they could and couldn't do in a different way. Badda bing, badda boom, your democratic republic at work.
I'm wondering if you are aware that there is ample evidence in the work of Adorno and his collegues (http://en.wikipedia.org/wiki/Authoritarian_personality), Lloyd deMause and the Institute for Psychohistory (http://www.psychohistory.com/) and Alice Miller (http://www.alice-miller.com/index_en.php) that political and military disasters are not linked to something intrinsic and inevitable in human nature, but rather to childhood and even prenatal experiences that can be avoided?
If you haven't, you might take a look at Lloyd deMause's book "The Emotional Life of Nations" (readable online: http://www.geocities.com/kidhistory/childhod/chindex.htm), which I think traces this ability of humans to murder and pillage to it's source and provides a plan for how it can be eliminated in the future.
Not quite, my theory is that the ability to commit atrocities is (much like I would assume your evidence would suggest) certainly evident in every being on the planet.
Mass atrocities and murder on large scales is simply a result of many people getting together, regardless of how they do so. Because it's the individual, and not the organization that is the actor, your point that "governments have murdered more people than corporations" is bunk. Given more power, any organization is capable of such crimes. For example, the Catholic Church.