“You're not to be so blind with patriotism that you can't face reality. Wrong is wrong, no matter who does it or says it.”

《乌克兰转型中的宪政权威》 ["The authority of the constitution in a Ukraine in transition"] (2004), translated by David Ownby in Rethinking China's Rise https://books.google.co.uk/books?id=761eDwAAQBAJ, p. 27

Source: Going Postal

Source: The Absolutely True Diary of a Part-Time Indian

Source: Speak

Interview, quoted in "Words from the Master" http://www.co.uk.lspace.org/books/apf/words-from-the-master.html in The Annotated Pratchett File http://www.co.uk.lspace.org/books/apf/index.html
General sources
Context: As for The Mapp... I suspect it'll never get a US publication. It seemed to frighten US publishers. They don't seem to understand it.
That seems to point up a significant difference between Europeans and Americans:
A European says: I can't understand this, what's wrong with me? An American says: I can't understand this, what's wrong with him?
I make no suggestion that one side or the other is right, but observation over many years leads me to believe it is true.

Rediscovering Lost Values http://mlk-kpp01.stanford.edu/index.php/kingpapers/article/rediscovering_lost_values/, Sermon delivered at Detroit's Second Baptist Church (28 February 1954)
1950s
Context: We have adopted in the modern world a sort of a relativistic ethic... Most people can't stand up for their convictions, because the majority of people might not be doing it. See, everybody's not doing it, so it must be wrong. And since everybody is doing it, it must be right. So a sort of numerical interpretation of what's right. But I'm here to say to you this morning that some things are right and some things are wrong. Eternally so, absolutely so. It's wrong to hate. It always has been wrong and it always will be wrong. It's wrong in America, it's wrong in Germany, it's wrong in Russia, it's wrong in China. It was wrong in 2000 B. C., and it's wrong in 1954 A. D. It always has been wrong, and it always will be wrong. It's wrong to throw our lives away in riotous living. No matter if everybody in Detroit is doing it, it's wrong. It always will be wrong, and it always has been wrong. It's wrong in every age and it's wrong in every nation. Some things are right and some things are wrong, no matter if everybody is doing the contrary. Some things in this universe are absolute. The God of the universe has made it so. And so long as we adopt this relative attitude toward right and wrong, we're revolting against the very laws of God himself. [... ] That attitude is destroying the soul of our culture! It's destroying our nation! The thing that we need in the world today is a group of men and women who will stand up for right and to be opposed to wrong, wherever it is. A group of people who have come to see that some things are wrong, whether they're never caught up with. And some things are right, whether nobody sees you doing them or not.

1860s, Allow the humblest man an equal chance (1860)
Context: But those who say they hate slavery, and are opposed to it, but yet act with the Democratic party — where are they? Let us apply a few tests. You say that you think slavery is wrong, but you denounce all attempts to restrain it. Is there anything else that you think wrong, that you are not willing to deal with as a wrong? Why are you so careful, so tender of this one wrong and no other? You will not let us do a single thing as if it was wrong; there is no place where you will allow it to be even called wrong! We must not call it wrong in the Free States, because it is not there, and we must not call it wrong in the Slave States because it is there; we must not call it wrong in politics because that is bringing morality into politics, and we must not call it wrong in the pulpit because that is bringing politics into religion; we must not bring it into the Tract Society or the other societies, because those are such unsuitable places, and there is no single place, according to you, where this wrong thing can properly be called wrong!

Colonel John Boyle and David in Ch. 7
Source: The Garden of Eden (1986)