“Justice will not be served until those who are unaffected are as outraged as those who are.”
According to a Snopes message board http://message.snopes.com/showthread.php?t=278, the earliest known reference dates to the late 1990s.
Misattributed
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Benjamin Franklin 183
American author, printer, political theorist, politician, p… 1706–1790Related quotes

“Justice is the first virtue of those who command, and stops the complaints of those who obey.”
As quoted in The Golden Treasury of Thought : A Gathering of Quotations from the Best Ancient and Modern Authors (1873) by Theodore Taylor, p. 227

“Justice is taking care of those who aren't able to take care of themselves.”
http://www.fool.com/news/commentary/2006/commentary06012002.htm

“Peace with justice means extending a hand to those who reach for freedom, wherever they live.”
2013, Brandenburg Gate Speech (June 2013)
Context: Peace with justice means extending a hand to those who reach for freedom, wherever they live. Different peoples and cultures will follow their own path, but we must reject the lie that those who live in distant places don’t yearn for freedom and self-determination just like we do; that they don’t somehow yearn for dignity and rule of law just like we do. We cannot dictate the pace of change in places like the Arab world, but we must reject the excuse that we can do nothing to support it.

1960s, Memorial Day speech (1963)
Context: The law cannot save those who deny it but neither can the law serve any who do not use it. The history of injustice and inequality is a history of disuse of the law. Law has not failed — and is not failing. We as a nation have failed ourselves by not trusting the law and by not using the law to gain sooner the ends of justice which law alone serves. If the white over-estimates what he has done for the Negro without the law, the Negro may under-estimate what he is doing and can do for himself with the law.

2000s, 2001, A Great People Has Been Moved to Defend a Great Nation (September 2001)

Letter to three students (October 1967) as translated in Solzhenitsyn: A Documentary Record (1970) edited by Leopold Labedz (1970) “The Struggle Intensifies".

Kitáb-i-`Ahd http://reference.bahai.org/en/t/b/TB/tb-16.html (Book of the Covenant)