Here's a great article written as a follow up from my article The Worldview Body Count. I, however, cannot claim to have authored this article. It was written by a fellow believer who is a follower of this ministry:

One of the major arguments commonly used by atheists against both Christianity and religion in general being allowed to have influence in the public sphere and being encouraged to 'proselytise'- is an argument based on the atrocities committed by Christians.

Typically the argument proceeds in a achetypal fashion as cited by Greg Koukl in his own book - Tactics:

Atheist: More wars have been fought and more blood has been shed in the name of God than any other cause. Religion is the greatest source of evil in the world.

In this case Koukl provides the correct response in citing the immense body counts of Secular Ideologies:

Koukl: You'll find that carnage of unimaginable proportions resulted not from religion but from institutionalized atheism: over 66 million wiped out by Lenin, Stalin and Khrushchev; between 32 and 61 million killed under Communist regimes since 1949; one third of the 8 million Khmers- 2.7 million people- were killed between 1975 and 1979 under the communist Khmer Rouge.

Koukl is correct in demonstrating the weakness of the atheistic position in just demonstrating the facts of history, clearly and with accuracy. However, such discussions rarely end there. Not because the atheist has a problem with the facts but because he has a problem with the categories used:

Atheist: Hang on, you can't claim that Stalin and Mao committed their crimes because of atheism. They never did this in the name of atheism or because they were motivated by atheism their crimes were unrelated.

In this case the atheist has merely reduced the scope of atheism to the point where any crimes committed by an atheist have no relation to atheism itself. Whereas religion is to blame if a perpetrator merely mentions God (see: Hitler, Breivik etc.), the relation between their actions and actual Christian doctrine is not relevant. There is an obvious double standard here and it highly useful to simply point it out, however now that the double standard has been established by the atheist his own tactic can be used against him.

In reducing the scope for the negative influences of atheism on the one hand, the atheist has unwittingly reduced the scope for all influences atheism has, this also includes positive influences. Therefore it is advantageous to demonstrate the tremendous positive influence Christianity has had throughout history in every sphere of life, because when the tables are turned atheism is completely naked as no-one commits these good acts in the name of atheism or with an atheistic motive. By the atheists own standard atheism is without utility.

Therefore the atheist has two choices; with the first option they need to re-expand the scope to the point that that the body count of the atheistic regimes is included, conceding the original argument and secondary argument. From this level of scope; atheism does not have any advantage on the 'body count' side of the coin and still loses out on the positive benefits ledger as well. The second option is to keep the revised scope and have to face reality that atheism offers no utility.

A positive aspect of including positives in such an argument. Is that Christianity can be framed as being being a beneficial philosophy as opposed to a 'lesser of two evils'. Which is a far better stance for evangelism.

Another weakness of the atrocity arguments is that the crimes are not just vast in their scope but also very recent. Considering all these events happened in recent memory atheism must be considered as a more dangerous belief system than Christianity in their modern forms. To illustrate; which man would you trust to keep sober? A man who got drunk years ago or a man who has lost control of his drinking recently? Given the relative rarity of atheistic regimes it is hard to see why atheists should oppose Christianity or religion in general due to past atrocities.

In the end, it should be noted, that this argument does not have any impact on whether atheism or Christianity is true. However it is a primary motivator behind militant atheism. If Christianity or religion in general can be demonstrated to be dangerous, it legitimizes aggressive atheism at a personal level as well as in politics which is where you get the fallacious 'separation of church and state' arguments being made.