Hitler atheism image
A 2016 Twitter (Ѻ) theist propaganda “atheism leads to Hitler” image, depicting some of the leading atheists of recent years, namely: T.J. Kincaid, Bill Maher, Richard Dawkins, Lawrence Krauss, Bill Nye, and Sam Harris.
In hmolscience, atheism atrocities fallacy, or “Stalin/Hitler debating point” (Dawkins, 2006), the theist's “trump card” (Ѻ), Reduction ad Hitlerum (Strauss, 1951) (Ѻ), among other names, is the assertion, typically employed in argument, that all large scale mass atrocities of history have been committed by atheists; something akin to the following assertion:
Nietzsche, Darwin, Hitler
This is a screenshot from a 2010 video (Ѻ) on how to beat an atheist in debate, point number six being to say "Hitler was an atheist" therefore godlessness leads to evil.

The fallacy, is the general statement that: Adolf Hitler (theist), Joseph Stalin (Marxist atheist), Vladimir Lenin, Mao Zeodong (secular Confucianist), and Pol Pot (secular Buddhist-Catholic) were all atheists and accordingly without morals engaged in mass acts of justified atrocity.

Hitler + Nietzsche | Stalin / Mussolini
Of note, Ravi Zacharias (2013) (Ѻ|13:40) asserts that Adolf Hitler presented copies of Friedrich Nietzsche to Joseph Stalin and Benito Mussolini personally. [3] Likewise, in his The Real Face of Atheism (2004) (Ѻ), Zacharias states that Hitler posed next to busts of Nietzsche in photos and that during Auschwitz Hitler, supposedly, said something along the lines of the following; which is said to be hanging on the wall of one of the Polish prison camps:

“I freed Germany from the stupid and degrading fallacies of conscience and morality. We will train young people before whom the world will tremble. I want young people capable of violence—imperious, relentless and cruel.”

In other places, however, Hitler seemed evoke morality:

“Secular schools can never be tolerated because such schools have no religious instruction, and a general moral instruction without a religious foundation is built on air; consequently, all character training and religion must be derived from faith ...we need believing people.”
— Adolf Hitler (1933), speech made during negotiations leading to the Nazi-Vatican concordant, Apr 26 (Ѻ)
Rheinhold's monkey (1893)
Vladimir Lenin, supposedly, kept a Hugo Rheinhold thinking Darwin monkey statue displayed on his desk in the Kremlin. (Ѻ)(Ѻ)

He also comments how Hitler, in his My Struggles, intermixed Nietzschean atheism with Darwinian atheism, and to assert the wrongfulness of interbreeding of weaker and stronger races; or something along these lines.

Philip Eveland (2000) corroborates (Ѻ) on this and moreover asserts that Hitler visited the Weimar Nietzsche archives several times and consumed Nietzsche’s philosophy as a baby consumes its mother’s milk; he also points out that Elizabeth, Nietzsche’s sister, congratulated Mussolini, on the occasion of his fiftieth birthday for being the ‘noblest disciple of Zarathustra.’

Bernice Rosenthal (2002) also, supposedly, discusses the “common Nietzschean elements” in the cults of personality of Stalin, Hitler, and Mussolini. (Ѻ)

Quotes
The following are related quotes:

“As an agent of our creator, by fighting off the Jews, I am doing the lord’s work.”
Adolf Hitler (1925), Mein Kampf (Ѻ)

“I do not believe that a decay of dogmatic belief can do anything but good. I admit at once that the new systems of dogma, such as those of the Nazis and the Communists, are even worse than the old systems, but they could never have acquired a hold over men’s minds if orthodox dogmatic habits had not been instilled in youth. Stalin’s language, e.g., is full of reminiscences of the theological seminary. What the world needs is not dogma, but an attitude of scientific inquiry, combined with a belief that the torture of millions is not desirable, whether inflicted by Stalin or by a deity imagined in the likeness of the believer.”
Bertrand Russell (1954), Human Society in Ethics and Politics [4]

“I admit that the generation which produced Stalin, Auschwitz and Hiroshima will take some beating, but the radical and universal consciousness of the death of god is still ahead of us. Perhaps we shall have to colonize the stars before it is finally borne in upon us that god is not out there.”
Reginald Hollingdale (1971), Thomas Mann: A Critical Study

“The grandfather of Marxian atheism and Freudian atheism is Ludwig Feuerbach, who was first a theologian, then a Hegelian, and finally an atheistic philosopher.”
— Hans Kung (1990), Freud and the Problem of God [2]

Stalin was an atheist and Hitler probably wasn’t; but even if he was, the bottom line of the Stalin/Hitler debating point is very simple. Individual atheists may do evil things but they don’t do evil things in the name of atheism.”
Richard Dawkins (2006), The God Delusion [1]

“I known you feel that religion has been a bane to civilization, but I feel that atheism has, and I will point to the worst mass-murders in modern times: Hitler, Stalin, Mao, and Pol Pot – all confirmed atheists.”
— Bill O’Reilly (2007), interview with Richard Dawkins (Ѻ)

See also
Atheism genealogy
Killing spree paradox

References
1. Dawkins, Richard. (2006). The God Delusion (pg. 378). Publisher.
2. Kung, Hans. (1990). Freud and the Problem of God (translator: Edward Quinn) (pg. 3). Yale University Press.
3. Zacharias, Ravi. (2013). “The Incoherence of Atheism” (Ѻ), City Life Church.
4. (a) Russell, Bertrand. (1954). Human Society in Ethics and Politics (pg. 208). Simon & Schuster.
(b) Hecht, Jennifer M. (2003). Doubt: A History: The Great Doubters and Their Legacy of Innovation from Socrates and Jesus to Thomas (pg. 453). HarperOne.

Further reading
● Murdock, Dorothy. (2010). “Were Stalin, Hitler and Pol Pot Atheists?” (Ѻ), Freethought Nation, Apr 17.
● Pearce, Jonathan. (2014). “A Great Myth About Atheism: Hitler/Stalin/Pol Pot = Atheism = Atrocity” (Ѻ), SkepticInk.com, Mar 3.
● Sherlock, Michael. (2014). “The Atheist Atrocities Fallacy” (Ѻ), RichardDawkins.net, Oct 23.

External links
Pol Pot and Mao Zedong were Not Atheists (2012) – Exposing Religion Blog.
Hitler, Stalin, and Atheism (2004) – RejectionOfPascalsWager.net.

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