I was born white, in California, so I have that culture's perspective. I've been called "cracker" more than once by a black man. The intent seemed offensive and intended to incite violence, but I let it slide at the time. (I try to shun violence, even when I've been drinking.) Once a Mexican fellow called me gabacho, but he was smiling, and corrected it to "my friend" when I stated larfing. I imagine he didn't mean to be TOO offensive; I could be wrong. I am fairly certain that my membership in the dominant ethnicity has affected my sensitivity to this sort of slight. OTOH I have known enough racist dickheads to understand why some people might be driven to some scarcely credible over-reaction to the existence and use of certain words. In the end, I don't see this having any lasting impact, some back-country schools and libraries will squander their public resources actually purchasing this landfill, but it won't have much intrinsic or collector value. I'd pay money for a copy of Jefferson's, or also Bowdler's version of the Bible, but this publication doesn't seem like a worthy item.
It's a shame this attitude exists, I'd love to see a faithful cinematic production of Huckleberry Finn. I've actually been thinking of this particular issue in light of the recent production of "True Grit". My thought was that we aren't ready for (worthy of?) Twain, (and this "news" proves it) but it's time for a remake of "Little Big Man".