Atheism's answer isn't communism, for one thing.
Totalitarian communist regimes suppress religion because of one person: Karl Marx. You know the famous "opium of the masses" quote? Here's more of it:
"Religion is the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions. It is the opium of the people. The abolition of religion as the illusory happiness of the people is the demand for their real happiness. To call on them to give up their illusions about their condition is to call on them to give up a condition that requires illusions. The criticism of religion is, therefore, in embryo, the criticism of that vale of tears of which religion is the halo."
In other words, according to Marx, oppressed people use religion to make their oppression bearable. If you remove their religion they will truly feel the suffering of their situation, and be spurred to rise up and revolt. Once socialism is in place and the people are no longer oppressed, they will no longer need religion.
Communist dictatorships have of course done little to alleviate the suffering of the people living in them. They see the persistence of religion as an outward sign of this, and thus pretending that the populace is happily irreligious by forcibly ousting religion becomes an ongoing requirement for international PR.
Marx may or may not be right about religion, but he could have told the Communists that forcing people to change, hide or cease their religious activities has little effect on their actual beliefs. (Incidentally, compare the terrible coercion by Communists to the peaceful activism which is now frivolously labeled "militant atheism". Compare that to "militant Islam" while you're at it.)
Communism's self-declared incompatibility with religion does not imply that atheism is responsible for the atrocities committed in the name of communism, even less than anti-Semitic atrocities can be laid at the feet of Christianity. This is because there are no atheistic commandments, no creed, no dogma, no central authority and certainly no "apostles". Nowhere does it say, "There are no gods, therefore do this and this." Communism declares that there are no gods while separately giving its followers commands, but does not link the two.
Atheism is a simple position on the existence of gods, a single conclusion and nothing more. It does not presume to contain answers to today's or any other era's problems. By precluding absolute trust in religious doctrine, however, it leaves one open to secular philosophies and moral systems, which provide earthly, tangible, verifiable rationales for their guidance. Those only interested in "power, wealth and materialistic pleasure" are not following these philosophies any more than they're following Christian morality.
On another topic, to Ruse's list of five "blots" on Christianity I would add three more:
- The continuing attacks on science and scientists in the interest of preserving the plausibility of Christian dogma, from Galileo to Darwin.
- The Thirty Years' War of the 17th century, fought between Christians with the singular goal of spreading people's own idea of God's Word.
- The continuing death of thousands in the Third and First Worlds as a result of intrinsically ineffective abstinence-only education and the defamation of condom use.
Not all crimes by atheists are due to atheism.
Not all crimes by theists are due to theism either, but some clearly are because they're done in the name of religion. The Crusades are a decent example, though their scale is disputed. The British knights went to the Middle East to take Jerusalem back, not for England, not for any kings, but for Christianity. They had crosses on their tabards, on their armour and on their shields. Their straight swords were often held upside down as crucifixes. They had to pray to become knights, and they prayed before battle. This is how you know the deeds were done in the name of Christianity.
Hitler and the Nazis were officially Catholic right to the end, but their deeds weren't done in the name of Christianity. They were done for National Socialism. I accept that just fine.
Now try to think of a battle fought "in the name of atheism". What does an atheist flag look like? What war song insults a god without offering another in its place? It's a silly idea.
Think of Communism in particular. It requires atheism, but it does not logically follow from atheism or else any atheist who really thought about it would be a Communist.
When Karl Marx wrote "religion is the opiate of the people", he was commenting on its effect on the populace, not its truth or falsehood. He thought of it as a painkiller. If religion were removed, he reasoned, the people would feel their pain sharply and be spurred to revolt. Afterwards they wouldn't need religion anymore, because in the new Golden Age they'd be happy without it.
Of course that's not how it turned out. Religion persisted because the people weren't happy at all under the new regimes. This was an indication to the outside world that the system wasn't working. It was good PR to squash religion as quietly as possible.
Also, the behavioural ideology of Communism is specific enough to conflict with that of any known religion. The authorities wouldn't take that kind of argument on their own turf. Communism became incompatible with religion on strict principle.
Finally, Communism is itself a quasi-religion. Its leaders are worshipped and even prayed to, its rules are absolute and its texts are immutable.
The faithful Russian, Chinese and North Korean soldiers and politicians who committed atrocities were atheists working in the name of Communism, just as the Nazis were Christians working for Nazism. Neither belief nor non-belief is accountable for either.
I think the problem is that people think because any country with a state religion or equivalent invokes that religion when going to war to boost approval, non-religious countries do the same thing with atheism. Atheism doesn't even work like that; it would be a terrible motivator all by itself.