“Slavery to State and men has disappeared only to make room for slavery to things and Self, to one's own vices and idiotic social customs and ways. Rapid civilization, adapted to the needs of the higher and middle classes, has doomed by contrast to only greater wretchedness the starving masses.”

Golden Sayings of Epictetus
Context: What you shun enduring yourself, attempt not to impose on others. You shun slavery—beware of enslaving others! If you can endure to do that, one would think you had been once upon a time a slave yourself. For Vice has nothing in common with virtue, nor Freedom with slavery. (41).

Source: 2010s, Why the Left Hates America (2015)

As quoted in [McInerney, Daniel John, The Fortunate Heirs of Freedom: Abolition & Republican Thought, https://books.google.com/books?id=ZrnV5Rj6eckC, 1994, U of Nebraska Press, 0-8032-3172-5, 83-4]

Source: The Evolution of Civilizations (1961) (Second Edition 1979), Chapter 9, Classical Civilization, p. 270

As quoted in "Ben Carson: Obamacare worst thing ‘since slavery’" https://www.washingtonpost.com/news/post-politics/wp/2013/10/11/ben-carson-obamacare-worst-thing-since-slavery/, Washington Post (October 11, 2013)

2000s, God Bless America (2008), Slavery and the Human Story
Context: But one may ask, how is it that slavery, or any other form of invidious discrimination, has played so great a role in American history? How could a nation, dedicated at its birth to the proposition that all men are created equal, have tolerated slavery and its effects so long? If we look to the long history of mankind, however, we will ask a different question. Slavery was lawful in every one of the original thirteen states. There was accordingly nothing remarkable in the fact that slavery was not abolished immediately on independence. What is remarkable is that a slave-owning nation would declare that all men are created equal, and thereby make the abolition of slavery a moral and political necessity. To accomplish that task would not be easy. We need to see the dimensions of that task to appreciate its difficulty.

Source: The Revolution Betrayed (1936), p. 40 in Doubleday, Doran & Company edition (1937)

Diary (5 June 1862)
Diary and Letters of Rutherford Birchard Hayes (1922 - 1926)
Context: These semi-traitors [Union generals who were not hostile to slavery] must be watched. — Let us be careful who become army leaders in the reorganized army at the end of this Rebellion. The man who thinks that the perpetuity of slavery is essential to the existence of the Union, is unfit to be trusted. The deadliest enemy the Union has is slavery — in fact, its only enemy.

Source: Give Me Liberty! (1998), Ch. 9 : Empowering the Self, p. 117