The idea that blacks were inferior was common for the time. It was common wisdom. It may have been wrong but it was certainly common. The idea that these are mutually exclusive with abolitionism is absurd. I'm sure there are many advocates for animal welfare who think they are superior to animals. It has never been the case that abolitionism was based on a desire for equality. It was based on a recognition of the inhumanity of slavery. Lincoln hated slavery but was certainly a man of his time and that is the way men of his time thought.