The answer is:
"They created the most effective public relations campaign in history, inventing techniques that we use to this day."
In the excerpt from "Sugar Changed the World," the author Marina Budhos makes reference to how Clarkson and other abolitionists made the abominations of the slavery system evident to those who made a profit out of it. For example, the exhibition of whips, handcuffs, testimonials and Equiano's memoir.