We’re up to number twenty-three. Hail Eris.
When confronted with all the brutality Christianity has inflicted on the world since it became the state religion of the Roman Empire under Emperor Constantine, an oft-heard rejoinder is "Well, what about Hitler, Stalin, Pol Pot, and Mao?"
Well, Hitler was a Christian, but Christians don’t want to hear that. If apologists don’t bring up Hitler, you shouldn’t either. (Aside from Godwin’s Law, there is no reason to create another point to argue over when refuting religious claims.)
Stalin, Mao, and Pol Pot frequently get brought up because the Soviet Union, Communist China (still), and Democratic Kampuchea all enshrined state atheism into their laws. In addition, communist political ideology generally disdains religion. In support of that, Karl Marx is quote mined by Christians (and others) to say something like "Religion is the opiate of the people."
The actual quote from Marx in full is a metaphor, and translated from German reads, "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"
Marx was implying by his metaphor that religion is response to oppression, not that religion was useless in and of itself or a tool of cynical politicians.
That said, state atheism is the position of a government that the foundation of the government is officially atheistic (as opposed to a theocracy: governance by religious bodies or figures, or secularism: governance disinterested in religious affairs). Examples of state atheism, theocracy, and secular governance might be (respectively) the Soviet Union, Iran (note Iran is a democracy, but its democracy is ordered by its religious leaders), and the United States.
Nations which practice state atheism generally do not allow religious people to be part of the government. For example, the Soviet Union’s constitutions allowed for freedom of religion. However, if you belonged to a religious body, you could not be a member of the Communist Party, and thus you could not be a member of the government. The same applies to the People’s Republic of China today.
Pol Pot and his Khmer Rouge were a paranoid autocratic regime that set about depopulating the cities of Cambodia to create an communist agrarian paradise, causing mass starvation, and slaughtering millions who were perceived to oppose the regime (whether they actually did or not). Education was held as a threat to the regime, so much so that people who wore glasses were killed (believed to be educated because they wore glasses).
Of note, Pol Pot’s regime was overthrown by another Communist nation, Vietnam, over masses of Cambodians fleeing over the border and the horrific human rights abuses of the Khmer regime.
The selection of Stalin, Pol Pot, and Mao are no accident by religious apologists (while they studiously ignore the USA’s Manifest Destiny, the Trail of Tears, and slavery, or the Inquisition, Thirty Years’ War, and the Crusades). Between those three men tens of millions of people were killed, possibly upwards of a hundred million.
They were not killed in the name of atheism though, which is why this is an apologetics fail. Those people were killed as a result of political opposition, or plain poor planning by state authorities (such as the mismanaged famine in Ukraine under Stalin).
The Crusades on the other hand were specifically mounted in the name of Jesus to kill heathens. The Fourth Crusade in particular can be remembered for its hypocrisy: It was mounted by Pope Innocent III to sack Jerusalem and take it from Muslims, but instead went awry and sacked the Byzantine Empire (a Christian nation).
So too was the Thirty Years’ War, the bloodbath across Europe between rising Protestantism and beleaguered Roman Catholicism in the fragmenting Holy Roman Empire (when the emperor tried to reëstablish Catholicism amongst the northern domains which were turning to Protestantism). Both sides slaughtered in the name of Jesus, pulling in all the European great powers of the day into the war over who’s version of God was the correct one.
Manifest Destiny in the USA, while not specifically driven by religious leaders, was the idea that the entirety of the North American continent was destined by God to be remade in the image of the original colonies. Those heathens in the way of that (Native Americans) were to be slaughtered to achieve a unified nation, or marched off to Oklahoma (the Trail of Tears under President Andrew Jackson). Chattel slavery was upheld with the Bible, and so on.
So the argument of "what about Stalin, Pol Pot, and Mao and the slaughters they perpetrated" is mere deflection or whataboutism. Their slaughters had nothing to do with religious belief, while Christian slaughters had everything to do with it.
The goal of defeating this apologetics fail should not be to try to rehabilitate Stalin, Pol Pot, or Mao, or get bogged down in the weeds over their atheism versus their authoritarianism. It should be immediately noted as a deflection and the argument returned to what brought on the deflection in the first place. Deflection is a dishonest debate or discussion tactic used when you cannot defend your position, and should be called out as such, with a notation that if they want to talk about Stalin, Pol Pot, and Mao, you’d be happy to do that in a different discussion.