Is it co-incidence that the world's worse mass murderers just happened to be atheists? Probably not.
Communism demanded that anyone who got in the way was liquidated. Now we should say, "Hang on a moment, just going around liquidating people is wrong and evil." But because communism was the highest authority, this objection didn't carry much force. A Christian, on the other hand, should be bound by a higher moral code that would strongly object to mass murder. Thus, although Stalin and Mao didn't kill because they were atheists, the fact they were atheists meant that they lacked the Christian moral compass that should have prevented them from taking the path they did.
Now anti-Christians will be jumping up and down and saying "I'm moral! I'm moral!" I'm sure you are. But your morality is secular humanism which is little more that Christianity without God and with more sex. If we replaced your democratic liberalism (which says be nice) with communism (which doesn't) what's going to stop you becoming mass murderers? Nothing except your residual post-Christian humanism. History fully bears out my contentions. When we look at the history of European socialism we see that the major split was between atheistic communism and Christian socialism. The later gave birth to the UK Labour Party, German Social Democrats and various other democratic socialist and social democrat parties. All have done enormous good in Western Europe. On the other hand, we know where the communists ended up. Of course there are plenty of atheist democratic socialists but their morals tend to be exactly the secular humanism they inherited from Christianity. That's why they rejected communism too.
What about all the atrocities committed by Christians? They were terrible, too. They were also committed by true Christians much of the time, but look what happens when you take away Christianity. Modern estimates suggest the Spanish Inquisition executed about 10,000 in three centuries. The anti-Christian Jacobins managed to execute three times that number in a mere three years of French revolutionary terror. And the inqusition still form the basis of European jurisprudence. I can't say the same for Jacobin show trials.
I think the main example that people have in mind of Christian crimes are the Eastern crusades. They get the impression that these were large scale wars. In fact they weren't and there were relatively few major engagements. We can't say that without the crusades no one would have been fighting anyone. Europeans might have been fighting each other. Religion determined who the enemy were rather than whether a war happened somewhere. 'Atrocities' during the crusades involved the three days of pillage allowed after a city had fallen by assault. This was the rule of war at the time and meant to encourage cities to surrender if they knew no relief was on the way. About 10,000 died in the fall of Jerusalem when it fell to the crusaders in 1099. In 1187, Christian Jerusalem surrendered in turn to Saladin and that is why he let many people go free on payment of a ransom. Many others were enslaved. Had Saladin taken the city by storm, he would have certainly been much less generous.
On some anti-Christian websites you'll see figures of millions of deaths given for the crusades, witch trials and inquisition. These are exaggerations by a factor of a hundred. The reason they peddle these lies is because they know that the actual figures for Christian crimes can't compare with atheist ones. Hence, they have to bump the figures up.
Comments or questions? Post them at Bede's dedicated yahoo group.