“Root out the counterrevolutionaries without mercy, lock up suspicious characters in concentration camps… Shirkers will be shot, regardless of past service.”

On ideas of eradicating 'counter-revolutionaries and traitors' in Estonia, as quoted in Stalin : A Biography (2004) by Robert Service, p. 158; also in Bol'shevistskoe rukovodstvo. Perepiska, 1912-1927, p. 36.
Contemporary witnesses

"Letter on Animal Liberation" (1999)

Source: Striking Thoughts (2000), p. 11

Chronicles of Dissent, December 13, 1989 http://www.zmag.org/chomsky/interviews/db-8912.html
Quotes 1960s-1980s, 1980s
Context: Non-violent resistance activities cannot succeed against an enemy that is able freely to use violence. That's pretty obvious. You can't have non-violent resistance against the Nazis in a concentration camp, to take an extreme case...

Part 3, Ch. 12, § 3.
The Origins of Totalitarianism (1951)
Context: The concentration camps, by making death itself anonymous (making it impossible to find out whether a prisoner is dead or alive), robbed death of its meaning as the end of a fulfilled life. In a sense they took away the individual’s own death, proving that henceforth nothing belonged to him and he belonged to no one. His death merely set a seal on the fact that he had never existed.

Simon Blackburn, Being Good (2001)

Paris Review (Summer 1966)
Context: If you complain of people being shot down in the streets, of the absence of communication or social responsibility, of the rise of everyday violence which people have become accustomed to, and the dehumanization of feelings, then the ultimate development on an organized social level is the concentration camp... The concentration camp is the final expression of human separateness and its ultimate consequence. It is organized abandonment.

Source: Pictures from an Institution (1954) [novel], Ch. 2, p. 66