In the mid 1700s a Virginian planter named Landon Carter stated that he abhorred slavery. George Mason, a founding father and a member of the Philadelphia convention, stated that slavery makes masters of slaves petty tyrants. However, before we bestow the MLK humanitarian award posthumously, we should probably add that Carter hated slavery because he hated Africans and their being in America. Mason was complaining about slavery's effects on whites not blacks, neither emancipated their slaves. Many people opposed slavery because of its effects on whites not blacks, but this letter isn't about slavery.
In ancient Greece, legend has it, there was an amicable chap named Procrustes. In his endeavor to provide guests with a hospitable visit, he provided weary travelers with a bed. Procrustes was somewhat obsessive compulsive and insisted that anyone sleeping in the bed must fit snugly, no space at the top, none at the bottom. Since there was no medication for his illness in those days, Procrustes did the only thing possible, he adjusted the length of the sleepers by either stretching their bodies or lopping off heads and feet. This isn't about Greek legends.
You cannot understand history by studying what people said, you need the context. In my opinion, there's an inverse ratio between people who quote the famous and their historical understanding of the same. History isn't about reading our own prejudices into the past; if you always find what you thought you would find, well, I'm hoping you've read the second paragraph.