The book isn’t constitution-focused, it’s founder-focused, and from the parts I have read the book spends more time with the convention than it does with the finalized constitution itself.
That clause is not really hard to deal with, of all people Frederick Douglass talks about it quite handily.
https://freerepublic.com/focus/f-chat/4026357/posts
Douglass: The American Constitution and the Slave: Is the Constitution pro-slavery or anti-slavery?
Douglass’s answer is that the Constitution is anti-slavery. Including A-IV S2.
Let's review.
A contributor in post 10 used a Lincoln quote and was admonished: “sigh and back to the civil war we go . . . I'm trying to talk about the Founding Fathers and The 1619 Project/progressives, that's all.”
Frederick Douglas was born in 1818; he is not a Founding Father. His most famous work was as an abolitionist before and during the war Lincoln, it is said, “fought to free the slaves.”
To be clear: Is this thread still about Founding Fathers and The 1619 Project or have you expanded it to include Lincoln-era figures?