“Since the adjournment of Congress the ratifications of the treaty with Great Britain for abolishing the mixed courts for the suppression of the slave trade have been exchanged. It is believed that the slave trade is now confined to the eastern coast of Africa, whence the slaves are taken to Arabian markets.”

morality
William Wilberforce (2007)
Variant: God Almighty has set before me two great objects, the suppression of the slave trade and the reformation of manners (morality).

2000s, God Bless America (2008), Slavery and the Human Story
Context: Slavery came to the English colonies in North America in the 17th century because the colonists found themselves in possession of a vast continent, needing only cultivation to make it the homes of millions of free, prosperous, God-fearing human beings. Those who came from Europe would be refugees from the tyranny and oppression of feudalism, divine right monarchy, and religious intolerance. But converting this vast wilderness into cultivated lands required labor. It was nearly inevitable that someone would turn to tribal Africa for some, at least, of this labor. It is paradoxical but true that a large measure of the labor that turned America into a sanctuary for freedom came from slavery. The slave trade that developed between North America and the west coast of Africa is one of the great horror stories of western civilization. It resulted also from the unlimited greed of the African chiefs who enslaved their brother Africans, and then sold them to white slave traders. They in turn sold them, for vast profits, into the new world.

They must feel at the same time the greater solicitude to give the fullest efficacy to their own regulations. With that view, the interposition of Congress appears to be required by the violations and evasions which it is suggested are chargeable on unworthy citizens who mingle in the slave trade under foreign flags and with foreign ports, and by collusive importations of slaves into the United States through adjoining ports and territories. I present the subject to Congress with a full assurance of their disposition to apply all the remedy which can be afforded by an amendment of the law. The regulations which were intended to guard against abuses of a kindred character in the trade between the several States ought also to be rendered more effectual for their humane object.
James Madison's Eighth State of the Union Address (3 December 1816)
1810s

June 17
Addresses to the Virginia Ratifying Convention (1788)

Source: The Wisdom of W.E.B. Du Bois (2003), p. 104

Letter to John Russell (5 October 1864), quoted in Jasper Ridley, Lord Palmerston (London: Constable, 1970), p. 544.
1860s

Opposition to the slave trade did come in time, in the principles of the American Revolution, but not before slavery had formed deep roots in the economy and polity of the United States. The foreign slave trade was outlawed by the United States in 1808, and it was made a capital crime in 1820, but the trade continued right up until the Civil War. It is good however to remind ourselves that no black slave was sold to a white slave trader, on the west coast of Africa, who had not already been enslaved by a black African. Slavery was an equal opportunity employer!
2000s, God Bless America (2008), Slavery and the Human Story

The Romance of Commerce (1918), A Representative Business of the Twentieth Century