Most of the counter arguments are based on the idea of the idea of the integrity of the author's work. That's a very valid concern, and one that I'm sure Gribben is alert to. It's what you might call the idealist position - we have to accept Huckleberry Finn, warts, niggers and all.
But, as I said, I think it misses the point. People are getting outraged over the symptom, rather than the disease. As Gribben pointed out, the book often isn't available in school libraries, and it isn't been taught; one of the absolute classics of American literature is being memory holed because schools are too scared - or too battle weary - to have anything to do with it.
Gribben is trying to reverse that, providing them with something that will retain 99.99% of the original, including the element of dehumanisation of Jim. This is what I'd call the pragmatist position.
The battle battle the Idealists want to fight has already been lost, because the book is gone from classrooms and school libraries. Gribben is trying to get it back there, salvage something from the rout of sanity in the culture wars.
Faced with the fact of the refusal of schools to stock an unexpurgated version, the pragmatist seeks a solution. The idealist sticks to some lofty principle of free speech and moral right; and loses by default.
If we get too hoity-toity and precious about it, take our niggers and go home, the status quo remains - and that's a victory for the barbarians, Flat Earthers, PC goons and identity politics junkies, unless we compel schools to stock certain books, which has similarly worrying overtones. With out resort to that extreme, the book will still be missing from school libraries and not being taught. Gribben's efforts, at least, mean the existence of Huckleberry Finn will be acknowledged.
I'm quite aware of the 'slippery slope' argument, and sympathetic to it (Wait until you see my edited version of Joseph Conrad's 'African of the Arcissus'). But I see this more as an effort to climb a bit of the way back up the slope, not helter-skelter further down it. A bigger battle is being lost than the excision of a single word from 'Huckleberry Finn' - the (hem) battle for good books in general.
1 - As described previously on lefthandpalm: http://lefthandpalm.blogspot.com/2011/01/with-regards-use-of-word-nigger-in.html