Phrenology, race and history

The movie Django Unchained includes a scene in which the antagonist (a rich, white, plantation owner) expounds on phrenology as a justification of slavery. James Poskett in The Guardian gives the historical context behind racist phrenology. The interesting part is the existence of anti-racist phrenology:

[I]t wasn't just the slavers. My research revealed that some of the most vocal anti-slavery campaigners of the 19th century were also advocates of phrenology, and used it to justify their stance.
Lucretia Mott, a particularly uncompromising American abolitionist, sent her children to phrenological lectures and spoke of the "truth of phrenology" in letters to friends. When she visited Britain she stayed with the renowned Scottish phrenologist George Combe, himself an anti-slavery campaigner. Horace Mann, another major figure in abolitionist politics, was so keen on phrenology that he subscribed to the official journal. After becoming president of Antioch College in Ohio, he even boasted in the same sentence that the professors he employed were both "anti-slavery men" and "avowed phrenologists".

The relation between science, pseudoscience, and highbrow morality in the nineteenth century was counterintuitive. Phrenologists were steampunk witchdoctors.