Peter (fl. 1863) (also known as Gordon, or "Whipped Peter", or "Poor Peter") was an escaped American slave who was the subject of photographs documenting the extensive keloid scarring of his back from whippings received in slavery. The "scourged back" photo became one of the most widely circulated photos of the abolitionist movement during the American Civil War and remains one of the most notable photos of the 19th-century United States.
I see where you're going with this and I accept the possibility Trump is just clumsy and avoidant on the issue.
But you must be aware that there is a strong belief amongst MAGA types and deep conservatives in general that slavery was benign if not beneficial to those subjugated. D'Souza wrote a whole book about it.
They believe liberals exaggerate the bad parts of slavery due to irrational white guilt and black people agree because they are whiners and want reparations.
I strongly suspect this plays into Trump's rants regarding museums and history curricula.