My point is that racism was the norm in Twains era and by no fault of his own, he also believed in it to a certain extent. Just read the scene near the end of Huckleberry Finn where Jim is captured and locked in a small shed while Huck and Tom work on an overly romantic plan to get him to escape. The whole time Jim obviously has no idea what is going on, but he goes along with them because he just assumes that they know better than he as to what to do. There’s even a line where Jim muses on the fact that they are white, so they must know what they’re doing.
Also, several times throughout the book, blacks are referred to as almost sub-human by some of the main “good” characters.