I agree with Rich Lowry at National Review:  Don’t rewrite Huck Finn.  When I read the book as a kid, I reached the same conclusion.  

It is Jim, the character who is demeaned and hunted like an animal, who
is most humane. While Huck?s father is an ignorant drunk who beats and
robs him, Jim desperately misses his own family, and his conscience
lashes him for having once hit his daughter unjustly. Huck reflects on
this and remarks, ?He was a mighty good n??, Jim was.?

Strike
the offending word from the text and you lose the point. The attitudes
of the time kept Huck from seeing what was obviously in front of him ?
simply a man, and a better one than most. Twain said that Huck had ?a
sound heart and a deformed conscience.? The boy?s triumph is rising
above the forces that shaped him and deciding to help Jim run away,
even though it?s supposed to be wrong. ?All right then, I?ll go to
hell,? he tells himself.

Huck thought ? because he was told by every adult around him ? that it
was a sin and a crime to free Jim and treat him as equal, and resolves
to do it anyway. It?s hard to imagine a more devastating critique of
antebellum America, or a more affecting portrayal of the power of human
fellow-feeling, than that. Please, don?t try to improve Huck Finn.