Q: Is government responsible for most of the deaths by violence and oppression in the 20th Century?
A: Well, yeah. Of course. Organized thugs kill more efficiently than disorganized thugs.
Wars and oppressions are collective endeavors, and whenever humans work collectively, they work through government. Whether wars are fought using citizen militia, standing armies, hired mercenaries, tribal warriors, corporate security teams, street gangs, paramilitaries or feudal levies, there's always a ruler or governing body to determine who does what to whom. Call it a cabinet, junta, council of elders, general staff, board of directors, politburo or capo de tutti capi -- it's a government.
Unfortunately, blaming war and tyranny on government is like blaming house fires on oxygen. Strictly speaking, it's true, but no fire marshal would ever get a good performance review if that's his answer to everything. To understand house fires, you'll have to look at wiring, storage, smoking, materials and cooking, and not just insist, "It's oxygen, I tell you! Oxygen is evil! Why won't anyone listen to me?"
Most attempts to blame government for democides depend on a kind of circular reasoning. They define "government" as any organization capable of mass violence, and then are amazed when all mass violence is produced by government. If they were to instead define "government" as, say, any organization that delivers mail or builds roads, then at least they would be moving away from obvious tautologies.
He makes a point that most people miss about the "militia", especially if they believe that being a part of an "Unorganised militia" qualifies them for dick. This is partially because they are ignorant that the "unorganised militia" is a draft pool of potential militia members. As I like to say, it's the equivalent of saying you are in the army because you have a draft card.
The really salient point is that the militias, especially during the War for American Independence, were under some form of government control. Despite the common criticism that they were as effective as a mob with sticks. The reality was that the militias and ultimately the Continental Army was under the Control of the Continental Congress and other forms of rebel government.
They weren't just some people who got together with weapons and beat off the British. In fact, the War for American Independence was both a civil war, in that the Loyalists had their own militias, and an actual war in that the British, French, Spanish, and various other countries were involved in fighting it.
So, you had both revolutionary miltia units and Loyalist militia units which were under some form of government control. They wern't unorganised bans of people who just struck out at "British tyranny" or "Rebel tyranny".
This puts the modern "militia" pretenders and Libertarian loonies in a quandry about the insurrection theory since how can one have tyranny in a democracy when one is technically the government? As Dennis v. United States, 341 U.S. 494 (1951) puts points out in regard to the insurrectionist theory:
The obvious purpose of the statute is to protect existing Government, not from change by peaceable, lawful and constitutional means, but from change by violence, revolution and terrorism. That it is within the power of the Congress to protect the Government of the United States from armed rebellion is a proposition which requires little discussion. Whatever theoretical merit there may be to the argument that there is a "right" to rebellion against dictatorial governments is without force where the existing structure of the government provides for peaceful and orderly change. We reject any principle of governmental helplessness in the face of preparation for revolution, which principle, carried to its logical conclusion, must lead to anarchy. No one could conceive that it is not within the power of Congress to prohibit acts intended to overthrow the Government by force and violence. The question with which we are concerned here is not whether Congress has such power, but whether the means which it has employed conflict with the First and Fifth Amendments to the Constitution.
So, there is no right to armed rebellion and one cannot make an argument that such a right exists where the existing structure of the government provides for peaceful and orderly change.