I love the restriction of range fallacy by which modern freethinkers and secularists try to stain Christianity and Judaisms with blood while trying to keep their own movement free from the taint of mass-murder.
Seeing that modern atheism arose as a reaction against the wars of religion in Western Europe after the collapse of confessional unity within the Patriarchate of Rome, it, as an indentifiable movement, is about 400 years old. I propose considering a body count for the first 400 years of each movement.
Let's see:
- The Christian Church. Let's be generous to the other side, and stretch it out to 500 years so we can count the riots by the Nitrian monks in Alexandria against our side, a few hundred dead.
- Judaism. It rather depends on where you start counting: If we start with Abraham, I think you get a few, say hundreds, dead in battle. If with Moses, rather bloodier with the conquest of Canaan, but still surely dead in the tens of thousands only. If with rabbinic Judaism after the fall of the Temple, I think you would need to investigate the degree to which Judaism and a religio licta in the Roman Empire participated in the persecution of the Church. Probably a few hundred dead tops.
- Modern atheism. Hundereds of millions dead. We can count not only the dead of Soviet, Chinese and Cambodian communism, but the tens of millions dead from "choice"--abortion on demand. (Don't try to squirm out on that one--they are biological humans, members of our species.)
- Islam. Even Islam which started out as a bloody religion of conquest did not manage to kill that many in its first 400 years.
Now, it may be objected that the population of the world is larger now. Ok, put in a scale factor of 100 against the monotheistic religions, and secularist atheism still out-kills by a large margin.
I shudder to think what the death-toll from secularist atheism will look like by the time it is as old as Christianity was when the 30-Years war ended.
Secular statism has certainly resulted in more deaths than religion, if only because the modern populations are higher, and weapons exist that can kill hundreds of thousands at a stroke.
But only religion has claimed to kill on the direct command of God.