This is from Thomas Sowell’s 2005 book Black Liberals, White Rednecks:
Themselves the leading slave traders of the eighteenth century, Europeans nevertheless became, in the nineteenth century, the destroyers of slavery around the world – not just in European societies or European offshoot societies overseas, but in non-European societies as well, over the bitter opposition of Africans, Arabs, Asians, and others. Moreover, within Western civilization, the principal impetus for the abolition of slavery came first from very conservative religious activists – people who would today be called “the religious right.” Clearly, this story is not “politically correct” in today’s terms. Hence it is ignored, as if it never happened.