"Here's the fatal flaw in Nazi ideology" - person who studied and documented the lives and crimes of top Nazis.

"Here's the fatal flaw in anti-Nazi ideology" - person who was raised by Nazis, named for a fictional Nazi ubermensch, which inspired pathological levels of inadequacy and insecurity as the animating force of his life's purpose, and much like Hitler, sought to drown out the noise of his pathologies through drugs and the flattery of sycophants.

Gee, that's a tough one.