Of course, by "lively discussion" I mean a bunch of theistards spouting nonsense and some intelligent people trying to
But there is a fairly easy analysis of the whole situation.
First, there's really nothing special or unusual about communist atrocities. Human history is steeped in blood; no race, no culture, no nation, no ideology is exempt. The Soviets had Gulags; the United States has imprisoned just as many people for the crime of excess melanin... not to mention enslaving them for a couple of centuries. Europe has colonialism, notably the Congo Free State. The only cultures, groups or ideologies without some egregious large-scale atrocity on their hands have merely lacked opportunity.
I mention this not (necessarily) to excuse these atrocities, but simply to place them in context. But it is true: communists have never taken a peaceful, prosperous society and run it into the ground. Pre-revolution Russia and China both were already pretty brutal places, teetering for centuries on the brink of famine, and in both societies many important measures of well-being improved substantially under communist rule.
It's true that communist societies — like every other powerful society — have perpetrated atrocities. It's also true that communist societies tend to be atheistic. The question though is whether there's a causal connection between atheism per se and the atrocities.
One standard for finding a specific causal connection is to ask: if X — and just X — were removed, how would the outcome differ?
There are two ways of answering this question: If the communists were not atheists, would they not have been communists? Would their communism have been substantially different? Robert's essay makes it plain that Marx and Lenin's anti-religion was a direct result of the clergy's complicity with German authoritarian and Tsarist rule. (And indeed we see the clergy's active participation in Hitler's anti-communist rule.) More importantly, because religion in general is not falsifiable, it can be used to justify anything. It is trivially easy to imagine that Soviet communists believed everything about communism except atheism in exactly the same detail. They would then have justified the exact same communism by saying, "God wants us to be communist."
Secondly, we have to ask, if the communists were God-communists instead of atheist communists, would they have perpetrated the same atrocities? Would God belief have somehow inoculated them against atrocity? Again, we have to answer in the negative. We have so many people — long before and long since communist rule, from the Inquisition to George W. Bush — justifying atrocity by appeal to religion that the idea that religion inoculates against atrocity is simply ludicrous.
Atheism is neither necessary nor sufficient for atrocity; there isn't even any discernible difference between atheist and religious atrocity. It is only the most ludicrous bias and deep-seated blindness that can connect one with the other.
Religion is not the root of all evil. Evil is the root of all religion.