You need not fantasize what I say, I write it out for you.
Actual history: There was chattel slavery in the US and it was legal under the original Constitution, which was later amended to outlaw same.
Actual history: Many of the founders owned slaves.
Alternate history: "Constitution and the founders were against slavery."
Can you tell the difference ?
Yes, we all know slavery existed and many of the founders had slaves. That does not mean that the founders wanted to keep it.
"All good men wish the entire abolition of slavery, as soon as it can take place with safety to the public, and for the lasting good of the present wretched race of slaves. The only possible step that could be taken towards it by the convention was to fix a period after which they should not be imported."
Oliver Ellsworth, December 10, 1787
"I believe a time will come when an opportunity will be offered to abolish this lamentable evil. Everything we do is to improve it, if it happens in our day; if not, let us transmit to our descendants, together with our slaves, a pity for their unhappy lot and an abhorrence of slavery."
Patrick Henry, letter to Robert Pleasants, January 18, 1773
"It is much to be wished that slavery may be abolished. The honour of the States, as well as justice and humanity, in my opinion, loudly call upon them to emancipate these unhappy people. To contend for our own liberty, and to deny that blessing to others, involves an inconsistency not to be excused."
John Jay, letter to R. Lushington, March 15, 1786
"Slavery naturally tends to destroy all sense of justice and equity. It puffs up the mind with pride: teaches youth a habit of looking down upon their fellow creatures with contempt, esteeming them as dogs or devils, and imagining themselves beings of superior dignity and importance, to whom all are indebted. This banishes the idea, and unqualifies the mind for the practice of common justice."
David Rice, speech to the constitutional convention of Kentucky, 1792
"Slavery, or an absolute and unlimited power in the master over the life and fortune of the slave, is unauthorized by the common law.... The reasons which we sometimes see assigned for the origin and the continuance of slavery appear, when examined to the bottom, to be built upon a false foundation. In the enjoyment of their persons and of their property, the common law protects all."
James Wilson, The Natural Rights of Individuals, 1804