Who kills more people, Atheists or Theists?

What an absolutely depressing question. In a world where most everyone agrees it would be a better place if people stopped killing other people, we are debating who kills more often.

However, since the point gets brought up often that evil communists, i.e. atheists, are responsible for killing hundreds of millions of people in the 20th Century, I wanted to look into that figure.
Here is a breakdown from one source. The author calculates that 262 million were killed in the 20th Century.
Of that figure, here is the breakdown of the 262 million killed. As you can note, it is not just the communists that killed people, it is also theist groups that added to the carnage. Now I maintain that communists did not kill people in the name of Atheistism. How can that be? After all, millions and millions of people died in Russia and China under communist governments — and those governments were both secular and atheistic, right? So weren't all of those people killed because of atheism — indeed, in the name of atheism and secularism?
No, that conclusion does not follow. Atheism itself isn't a principle, cause, philosophy, or belief system which people fight, die, or kill for. Being killed by an atheist is no more being killed in the name of atheism than being killed by a  Mathematician. The communists accepted Atheistism, there is no doubt of that. However, they also accepted math. I am sure no one believes they killed in the name of math. Communists killed in the name of their state totalitarianism. Any government that takes total control of a society is bad. That is true whether it is atheists or theists who take control. Communism is actually very similar to Theism. It elevated the state to the level of god in their society.

But why would theist governments also kill people? They claim to follow the word of the deity, and in most religions, killing is prohibited.

The Deka-Megamurderers ... 219.634 million:

China (PRC) 1949-87 .... 76.702 million

U.S.S.R. 1917-87 ........ 61.911 million

Colonialism .............. 50.000 million

Germany 1933-45 ....... 20.946 million (including 5.291 million Jews)

China (KMT) 1928-49 ... 10.075 million

The Megamurderers .... 19.180 million

Japan 1936-45 ............ 5.964 million

China (Mao Soviets) 1923-48 ... 3.468 million

Cambodia 1975-79 ........ 2.035 million

Turkey 1909-18 ........... 1.883 million

Vietnam 1945-87 .......... 1.647 million

Poland 1945-48 ........... 1.585 million

Pakistan 1958-87 ......... 1.503 million

Yugoslavia (Tito) 1944-87 ... 1.072 million

Fatal regimes. Add the mega-massacres with the other genocides, purges and mass killings, and Rummel comes up with a 20th century death toll by abusive governments of 262 million.

http://frankwarner.typepad.com/free_frank_warner/2006/05/dictatorships_d.html

However, the question that gets glossed over by Christians is simple. They believe that communists killed people because they do not believe in god. Why, then, did theists (Christians) kill people in mass numbers as well? I am sure someone will say, they were not real Christians. That is simply a dodge. If belief in Jesus changes someone, then we should rarely see Christians kill people. And that is just not the case. Besides, I can just as easily claim that the communists were not real Atheists.

And since it is only in the 20th Century that there have been countries with atheist governments, then all the killing that has been happening for the past 5,000 years has been the responsibility of theist governments. How many people were killed before the 20th Century? Since there were not any groups keeping specific numbers, we shall never really know. But i will wager that the number far surpasses what was done in the 20th Century.