Did they and their genocidal regimes commit atrocities BECAUSE of atheism or were they persecuting religious people because they wanted to maintain power and have no competition? Rhetorical question, it's the latter. They may have been atheists, but when they removed God they effectively inserted themselves in his place, then committed atrocities in order to maintain control, and gain power over their enemies.
Discussion
You’re right that regimes like the Soviets and Communist China committed atrocities to maintain power, but removing God made that kind of unchecked power possible. Without a higher moral authority, they weren’t just suppressing rivals, they were eliminating any competing source of truth, meaning, or accountability. Atheism wasn’t the sole motive, but it created the vacuum where the state could become absolute and conscience could be crushed without restraint.
The same pattern is true of much religious violence throughout history. It was often about control, not genuine faith. Leaders used religion as a tool to legitimise their power and eliminate competition. That wasn’t obedience to God, it was a distortion of belief for political gain.
The difference is this: when religious violence happens, it usually violates the core teachings of the faith, especially in Christianity, where Christ taught love, mercy, and nonviolence. But when atheistic regimes commit violence, they aren’t violating their worldview, they’re often acting entirely in line with it. Without God, there’s no moral limit to what can be justified in the name of progress or power.
There are a few fallacies here, but I only need to address one, the one at the very end. Atheism doesn't have a worldview. Atheism is simply describing a lack of religious belief. It would have a worldview the same way "off" is a television channel or that "bald" is a hair color.
What worldview would you assign to people who choose not to participate in the hobby of collecting stamps? What attributes could you reliably assigned to that group of people? Same thing with atheists.
I get the analogy, but it doesn’t quite hold up. Choosing not to collect stamps doesn’t shape how you view morality, human dignity, or the meaning of life. But denying the existence of God does touch all those things. Atheism might begin as a lack of belief, but when that lack becomes the foundation of your view of reality, it functions as a worldview whether it claims to or not.
Once you remove God, you're left with big questions: What grounds morality? What gives life value? What defines right and wrong? You must answer those somehow, and the way you do it forms a worldview. That’s why many atheists gravitate toward naturalism, humanism, or moral relativism. Not all answer these questions the same way, but they can't avoid answering them.
So while atheism might not prescribe a worldview, it inevitably shapes one. And when it’s the organising principle of a political regime, as it was in Stalin’s USSR or Mao’s China, it becomes much more than a personal belief. It becomes a framework for power, ethics, and human worth, and history shows the consequences of getting those answers wrong.