Two sources for a very simple Red Pill on this topic:

http://hawaii.edu/powerkills/NOTE1.HTM

Death by Government, by R. J. Rummel

Rummel spent his career researching murder by governments. His well-documented conclusion: Governments in the 20th century murdered over a quarter-billion people (mostly "their own" citizens). That is IN ADDITION to war dead.

Edit: And on Communist governments specifically, see

The Black Book of Communism: Crimes, Terror, Repression

BTW, the Foreward is titled "The Uses of Atrocity"

Two sources for a very simple Red Pill on this topic:

http://hawaii.edu/powerkills/NOTE1.HTM

Death by Government, by R. J. Rummel

Rummel spent his career researching murder by governments. His well-documented conclusion: Governments in the 20th century murdered over a quarter-billion people (mostly "their own" citizens). That is IN ADDITION to war dead.