Following up on posts on Marxism and its fellow travelers (Engels, Mao, Guzmán, Hobsbawm), a question about whether Marxism’s brutal history is a built-in consequence of its principles or an accidental by-product of well-intentioned theory. So a series of quotations (with sources) from some principal figures:
Marx in 1848: “there is only one way in which the murderous death agonies of the old society and the bloody birth throes of the new society can be shortened, simplified and concentrated, and that way is revolutionary terror.”[1]
Engels in 1849: “The next world war will result in the disappearance from the face of the earth not only of reactionary classes and dynasties, but also of entire reactionary peoples. And that, too, is a step forward.”[2]


Lenin in 1917: “The state is an instrument for coercion … We want to organize violence in the name of the interests of the workers.” And in 1920: “A good Communist is at the same time a good Chekist.”[3]
Dzerzhinsky, Cheka chief, in 1918: “The public and the press misunderstand the character and tasks of our Commission. We stand for organized terror — this should be frankly stated — being absolutely indispensable in current revolutionary conditions.”[4]


Trotsky on Stalin in 1940: “Under all conditions well-organized violence seems to him the shortest distance between two points.”[5]
So in explaining the enormous death toll in communist societies in the twentieth century, we have two options:
Option 1. Communism is a humane theory, but its practitioners somehow mis-interpreted Marx and/or things got out of control unintentionally.
Option 2. Communism is a theory that calls explicitly for terrorism and the extermination of people.

Sources:
[1] Karl Marx, “The Victory of the Counter-Revolution in Vienna,” Neue Rheinische Zeitung No. 136, November 1848. [2] Friedrich Engels, “The Magyar Struggle,” first published in Neue Rheinische Zeitung No. 194, January 13, 1849. [3] Vladimir I. Lenin, quoted in George Leggett, The Cheka: Lenin’s Political Police, Oxford University Press, 1987. [4] Felix Dzerzhinsky, press interview in early June 1918, quoted in Leggett, The Cheka. [5] Leon Trotsky, Stalin – An Appraisal of the Man and his Influence, unfinished manuscript published in 1941.
Related: On the New Left turn to violence: “The Crisis of Socialism” [pdf], Chapter 5 of Explaining Postmodernism: Skepticism and Socialism from Rousseau to Foucault. Post: Soviets and Nazis — which were worse?
On the violence-necessitating philosophy underlying Marxism:
A close reading of the basic text for Marxists: