Reductio ad Hitlerum

Reductio ad Hitlerum (pseudo-Latin for "reduction to Hitler"; sometimes argumentum ad Hitlerum, "argument to Hitler", ad Nazium, "to Nazism"), or playing the Nazi card, is an attempt to invalidate someone else's position on the basis that the same view was held by Adolf Hitler or the Nazi Party, for example: "Hitler was a vegetarian, X is a vegetarian, therefore X is a Nazi". A variation of this fallacy, reductio ad Stalinum, also known as "red-baiting", has also been used in political discourse.

Coined by Leo Strauss in 1951, reductio ad Hitlerum borrows its name from the term used in logic, reductio ad absurdum (reduction to the absurd). According to Strauss, reductio ad Hitlerum is a form of ad hominem, ad misericordiam, or a fallacy of irrelevance. The suggested rationale is one of guilt by association. It is a tactic often used to derail arguments, because such comparisons tend to distract and anger the opponent, as Hitler and Nazism have been condemned in the modern world.

Reductio ad Hitlerum is a form of association fallacy. The argument is that a policy leads to – or is the same as – one advocated or implemented by Adolf Hitler or the Third Reich and so "proves" that the original policy is undesirable.

Another instance of reductio ad Hitlerum is asking a question of the form "You know who else...?" with the deliberate intent of impugning a certain idea or action by implying Hitler held that idea or performed such action.

An invocation of Hitler or Nazism is not a reductio ad Hitlerum when it illuminates the argument instead of causing distraction from it.

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Wikipedia