“The organization of federal units of black soldiers, comprised of both escaped slaves and free men, was taken as an outrage. It struck a raw nerve, never far off in the southern psyche. Fear of a slave insurrection. The prospect of African American men in blue uniforms was taken as an extreme provocation, so much so that it was proposed in the Confederate congress, and endorsed by General Beauregard, the hero of Fort Sumter, that all Federals captured, black or white, should be summarily executed. This proposal was never adopted, but the Confederate congress did eventually pass, in May 1863, a proclamation instructing President Jefferson Davis to exercise 'full and ample retaliation' against the north for arming black soldiers. Finally, there was simple revenge. The Union army's shelling of Fredericksburg several months before had been a particular sore point, that festered for months as the Confederate army went into winter quarters nearby. One officer, determined to fix the destruction there in his mind's eye, made a special visit to that town one last time before setting out on the road north into Maryland and Pennsylvania.”

As quoted in His Brother's Blood: Speeches and Writings, 1838–64 https://books.google.com/books?id=qMEv8DNXVbIC&pg=PA170 (2004), edited by William Frederick Moore and Jane Ann Moore, p. 170
1850s, The Fanaticism of the Democratic Party (February 1859)

Black Women Writers at Work (1983) by Claudia Tate

Source: The Killer Angels

1860s, Should the Negro Enlist in the Union Army? (1863)

2000s, The Real Abraham Lincoln: A Debate (2002), The South was a Closed Society
Context: There were eight of them that had laws trying to protect black people who were free from being kidnapped as slaves, because under the law of 1850, the Fugitive Slave Act. If a Southerner came across from Virginia to Pennsylvania and saw a black man that he thought he would like to have as a slave, he had to say, 'Well, that’s my runaway slave', and this runaway slave would then be arrested and confined, and then there would be a hearing before a federal commissioner. And the would-be slave owner could summon witnesses—as many as he wanted. The man accused of being a slave could summon no witnesses, had no counsel. And if the federal commissioner decided he was a slave, he was paid $10, and if he decided he was a free man, he was paid $5. It’s hard to imagine any law passed in either Nazi Germany or Stalin's Russia that was more inconsistent with the principles of civil liberty than the Fugitive Slave Act.

Letter to the Soldiers of Coroticus (c.450?)
Context: Because of all this, I am at a loss to know whether to weep more for those they killed or those that are captured: or indeed for these men themselves whom the devil has taken fast for his slaves. In truth, they will bind themselves alongside him in the pains of the everlasting pit: for "he who sins is a slave already" and is to be called "son of the devil."

My Race (1893)
Context: Ostentatious men who are governed by self-interest will combine, whether white or black, and the generous and selfless will similarly unite. True men, black and white, will treat one another with loyalty and tenderness, out of a sense of merit and the pride of everyone who honors the land in which we were born, black and white alike. Negroes, who now use the word "racist" in good faith, will stop using it when they realize it is the only apparently valid argument that weak men, who honestly believe that Negroes are inferior, use to deny them the full exercise of their rights as men. White and black racists would be equally guilty of racism.

2000s, Intelligence Report: Rebels With A Cause (2000)