"“There was no law mandating slavery on our shores when African slaves came ashore in 1619. Did slavery already exist in the world? Of course. But not in the laws of colonial America at the time,” Kaine explained. “We could have been a nation completely without the institution. But colonial legislatures and courts, and eventually the U.S. legal system, created the institution on our shores and maintained slavery until the 13th Amendment. As I said, we didn’t inherit it. We chose to create it.”
Sounds rational to me.