Jefferson was in some ways the least orthodox and the most skeptical of the founders. Yet when he condemned slavery he found himself using biblical language. In Notes on the State of Virginia Jefferson warned that those who would enslave people should reflect that "the Almighty has no attribute which can take side with us in such a contest." Jefferson famously added, "And can the liberties of a nation be thought secure when we have removed their only firm basis, a conviction in the minds of the people that these liberties are the gift of God? That they are not to be violated but with His wrath? Indeed I tremble for my country when I reflect that God is just: that His justice cannot sleep for ever."
But wasn't Jefferson also a man of science? Yes he was, and it was on the basis of the latest science of his day that Jefferson expressed his convictions about black inferiority. Citing the discoveries of modern science, Jefferson noted that "there are varieties in the race of man, distinguished by their powers both of body and of mind...as I see to be the case with races of other animals." Blacks, Jefferson continued, lack the powers of reason that are evident in whites and even in native Indians. While atheists today like to portray themselves as paragons of equal dignity, Jefferson's scientific and skeptical outlook contributed not to his anti-slavery sentiments but to his racism. Somehow Harris and Shermer neglect to point this out.
In the end the fact remains that the only movements that opposed slavery in principle were mobilized in the West, and they were overwhelmingly led and populated by Christians. Sadly the West had to use force to stop slavery in other cultures, such as the Muslim slave trade off the coast of Africa. In some quarters the campaign to eradicate slavery still goes on.
So who killed slavery? The Christians did, while everyone else generally stood by and watched.