“Because we have sought to cover up past evil, though it still persists, we have been powerless to check the new evil of today.
Evil unchecked grows, Evil tolerated poisons the whole system.”

1960s, Keep Moving From This Mountain (1965)
Context: And now it is time for us to move on to that great and noble realm of justice and brotherhood. That is the great struggle taking place in our nation today. It isn’t a struggle just based on a lot of noise; it is a struggle to save the soul of our nation for no nation can rise to its full moral maturity so long as it subjects a segment of its citizenry on the basis of race or color. And somehow we must come to see more than ever before that racial injustice is a cancer in the body politic which must be removed before our moral health can be realized. Racial segregation must be seen for what it is — and that is an evil system, a new form of slavery covered up with certain niceties of complexity. [... ] Segregation is evil because it relegates persons to the status of things. [... ] And segregation is evil because it stigmatizes the segregated as an untouchable in a caste system. We’ve been in the mountain of segregation long enough and it is time for all men of goodwill to say now, “We are through with segregation now, henceforth, and forever more.”

Source: Brisingr

The Way of God's Will Chapter 1-4. Practice http://www.unification.org/ucbooks/WofGW/wogw1-04.htm Translated 1980.

1950s, The Birth of a New Nation (1957)

Source: The Courtship of Princess Leia

2000s, Thus Spake Stallman (2000)
Context: If in my lifetime the problem of non-free software is solved, I could perhaps relax and write software again. But I might instead try to help deal with the world's larger problems. Standing up to an evil system is exhilarating, and now I have a taste for it.

Source: Letters and Papers from Prison (1967; 1997), Are we still of any use?, p. 16.
Context: We have been silent witnesses of evil deeds: we have been drenched by many storms; we have learnt the arts of equivocation and pretence; experience has made us suspicious of others and kept us from being truthful and open; intolerable conflicts have worn us down and even made us cynical. Are we still of any use? What we shall need is not geniuses, or cynics, or misanthropes, or clever tacticians, but plain, honest, straightforward men. Will our inward power of resistance be strong enough, and our honesty with ourselves remoreseless enough, for us to find our way back to simplicity and straightforwardness?

Non-Violent Resistance - Often misquoted as "You assist an evil system most effectively by obeying its orders and decrees. An evil system never deserves such allegiance."
Posthumous publications (1950s and later)
Context: You assist an unjust administration most effectively by obeying its orders and decrees. An evil administration never deserves such allegiance. Allegiance to it means partaking of the evil.
A good person will resist an evil system with his whole soul. Disobedience of the laws of an evil state is therefore a duty.

A Vindication of Natural Society (1756)
Context: We scarce ever had a prince, who by fraud, or violence, had not made some infringement on the constitution. We scarce ever had a parliament which knew, when it attempted to set limits to the royal authority, how to set limits to its own. Evils we have had continually calling for reformation, and reformations more grievous than any evils. Our boasted liberty sometimes trodden down, sometimes giddily set up, and ever precariously fluctuating and unsettled; it has only been kept alive by the blasts of continual feuds, wars, and conspiracies.