Bowdlerizing a work like that means you don't really understand it. One might as well have Jim speaking in iambic pentameter so no one will be offended by his uneducated speech. It's supposed to be rough, brutal, and offensive, because that's what Twain was trying to describe. The entire point of the novel is encapsulated when Huck ceases to regard Jim as a sub-human and recognizes him as a friend. Twain allows Jim enough silliness to make him as human as the other characters. To manage all of that in the voice of an adolescent boy is high art, and it isn't improved by Disney-izing it. IMHO.