Briefly, we can see Huck's relationship with Jim as more-or-less a relationship of equals. Huck articulates his recognition that Jim loves his wife and family as much as any one else loves their family, regardless of skin color.
"I do believe he cared just as much for his people as white folks does for their'n. It don't seem natural, but I reckon it's so."
Huck recognizes also Jim's kindness and generosity, given freely and outside of any formal context.
Also, the commentary made by Pap Finn early in the novel regarding a clean-shirted free African American functions as an ironic indictment of racism. Pap's vehemence and resentment work against him and demonstrate the hypocrisy of his racist sentiments.
These are anti-racist sentiments.
Pap's pettiness and racism are mirrored later. Jim's treatment at the Phelps farm (both before and after the attempted escape) is inhumane, lacking common respect, and presupposing of a status quo which takes this kind of treatment for granted.
These are racist sentiments.