“The art of politics is judging what circumstances permit and what they forbid. Look at the reputation of, say, John Brown and the abolitionists before the Civil War. Lincoln had very harsh things to say about John Brown in 1859. The Civil War vindicated John Brown.”

Responding to a heckler. (from John A: The Man Who Made Us by Richard J. Gwyn).
Undated

1860s, Speech at Hartford (1860)

If They Come in The Morning (1971)

Regarding John Brown, as quoted in A Lecture On John Brown http://memory.loc.gov/cgi-bin/ampage?collId=mfd&fileName=22/22002/22002page.db&recNum=9&tempFile=./temp/~ammem_rvc6&filecode=mfd&next_filecode=mfd&prev_filecode=mfd&itemnum=2&ndocs=32

As quoted in Lies My Teacher Told Me: Everything Your American History Textbook Got Wrong https://books.google.com/books?id=5m2_xeJ4VdwC&printsec=frontcover&dq=lies+my+teacher+told+me&hl=en&sa=X&ei=dV39VNWyPMmWgwTN14JQ&ved=0CCwQ6AEwAA#v=snippet&q=maltreated&f=false (2008), p. 193
2000s, 2007, Lies My Teacher Told Me: Everything Your American History Textbook Got Wrong (2007)
Context: Ideas made the opposite impact in the Confederacy. Ideological contradictions afflicted the slave system even before the war began. John Brown knew the masters secretly feared their slaves might revolt, even as they assured abolitionists that slaves really liked slavery. One reason his Harpers Ferry raid prompted such an outcry in the South was that slave owners feared their slaves might join him. Yet their condemnations of Brown and the 'Black Republicans' who financed him did not persuade Northern moderates but only pushed them toward the abolitionist camp. After all, if Brown was truly dangerous, as slave owners claimed, then slavery was truly unjust. Happy slaves would never revolt... White Southerners founded the Confederacy on the ideology of white supremacy. Confederate soldiers on their way to Antietam and Gettysburg, their two main forays into Union states, put this ideology into practice: they seized scores of free black people in Maryland and Pennsylvania and sold them south into slavery. Confederates maltreated black Union troops when they captured them.

This was written on a note that he had at his execution (2 December 1859), most sources say it was handed to the guard, but some dispute that and claim it was handed to a reporter accompaning him; as quoted in John Brown and his Men https://books.google.com/books?id=uiaYWp66b-cC&pg=PR1&dq=John+Brown+and+his+Men+%281894%29+by+Richard+Josiah+Hinton&hl=en&sa=X&ei=Uub_VN3CN5HbggTdxIK4Cw&ved=0CB4Q6AEwAA#v=onepage&q=John%20Brown%20and%20his%20Men%20(1894)%20by%20Richard%20Josiah%20Hinton&f=false (1894) by Richard Josiah Hinton, p. 398.

In Selected Papers of Thaddeus Stevens

http://www.heraldsun.news.com.au/common/story_page/0,5478,10782838%255E1702,00.html

1990s, The Party of Lincoln vs. The Party of Bureaucrats (1996)
Context: The civil rights establishment, led by the NAACP, fought the good fight that led to the Brown v. Board of Education decision in 1954 and the Civil Rights Acts of 1964 and 1965. They fought that fight under the banner of the Equal Protection Clause of the 14th Amendment, which reflected the equality proclaimed in the Declaration of Independence. The classic statement of this principle is to be found in Justice John Marshall Harlan's dissenting opinion in Plessy v. Ferguson, the infamous 1896 decision that enshrined "separate but equal" into constitutional law for more than half a century, "In view of the Constitution, in the eye of the law, there is in this country no superior dominant ruling class of citizens. There is no caste here. Our Constitution is color blind, and neither knows nor tolerates classes among citizens. In respect of civil rights, all citizens are equal before the law. The humblest is the peer of the most powerful. The law regards man as man, and takes no account of his surroundings or of his color when his civil rights as guaranteed by the supreme law of the land are involved".