I get the impression that the Anne Frank thing is of a very different order. I can't imagine readers of Twain being left in much doubt as to what 'slave' refers to, while to utterly change the intention and content of a book is very different. A bit like the recent Arabic translations of Mein Kempf.
For me, it's fascinating that something like Lady Chatterley's Lover was unpublished until about 50 years ago; now we're arguing about the use of the word nigger, a word I'm deeply uncomfortable saying. I think that's the bottom line really - if I was comfortable saying nigger in public then I'd see no reason to censor it. I'm not saying it's not ridiculous, because I think people are intelligent enough to cope with it, but it's one of the most politically sensitive words in American English, so it's not really that surprising or offensive that it has been censored, to me.
