Reductio ad Hitlerum Guide, Meaning , Facts, Information and Description
This term was originally coined by University of Chicago Classics professor and ethicist Leo Strauss.The "reductio ad Hitlerum" fallacy is a special case of the genetic fallacy, of the form "Adolf Hitler, or the Nazi party, supported X, therefore X must be evil".
The fallacious nature of this argument is best illustrated by identifying "X" as something that Adolf Hitler or his minions did support but is not considered evil, setting X="vegetarianism" or X="breathing in and out". Those policies advocated by Hitler and his party which are generally considered evil, can all be condemned on other, logically more sound, grounds.
Example
The President supports tax cuts, but so did Hitler. I don't support the president's pro-Hitler agenda.