This isn't an easy matter. The New Jersey Star-Ledger collects some online responses, including this very touching one by "Rose" at Feministing:
Nonetheless, delicate though our sensibilities may be, we just can't get behind a bowdlerized Huckleberry, any more than we can a Shakespeare bowdlerized by Bowdler himself. ("Out, crimson spot" indeed!).
Whether or not "all modern literature comes" from this one book -- and it may, but it may not -- there is no question that Huckleberry Finn is among the most important novels of its time, and a critical text in the work of one of the few essential American writers. And it is, as Hemingway understood perfectly well, modern. It is not a work which comes from the dim mists of prehistory, laden with the prejudices of its time, which must simply be forgiven in order to appreciate its beauties.
On the contrary: the central beauty of Huckleberry Finn is its readiness to offend. It offends the racial assumptions of Americans, both Southern and Northern. And it uses offensive language to do that, sharpening the point in order to drive it home. This, for the most part, is why people get upset about it these days.
But even beyond race, it offends the easy Victorian sentimentalization of family -- Huck's father is a violent drunk, remember? It offends anybody who wants literature to be "nice," and it offends in particular anybody who makes the mistake of considering Huckleberry Finn as "children's literature." At one time or another, most of us are fooled by the fact that Huckleberry Finn includes characters borrowed from Tom Sawyer. But then we read a few chapters, and figure it out: this book is no more intended for children than Moby Dick or The Turn of the Screw. (The author himself made this point, and was much funnier than we will ever be.)
The pedagogical solution, then, is not to dumb the book down for the use of our wee widdle kiddie-widdies. The solution is to teach the book to adults. And, if a child does happen to stumble over it -- not in the classroom, from which it is exiled, but perhaps in the musty stack of paperbacks at a yard sale, alongside Macbeth and Billy Budd and Fahrenheit 451 -- snatch it from the little brat's hands at once, and lock it away until she is old enough to drink, smoke and vote.