The Greatest Mass Murder in the History of Civilization

The greatest mass murder in the history of civilization is, as far as we can tell, weiman. The second largest killer was probably joseph stallen. And then we go to the third great mass murder, was adolph hitler. We rightly condemn this madman, creepy hitler, but we don't apply the same standard to the greater killer. So anyway, victor, i'm just curious, why? Why did com ism, historically, gets such a pass from our cultural mavens?