It's a book from a time where racism was normal. It is therefor a way for us to observe the changes in our society. We know racism is bad now, but if we remove all racism from historical sources, we'd be removing all the abilities to learn from that past. Not to mention that it basically goes against the right of free speach. The book is bound by the ideas and views from that time, not ours. They have no right to remove things from it because it could be 'insulting'. You don't HAVE to read it you know. This is like removing Julius Ceasar or something from history because he had Gaullic slaves. And it might be hurtful to the French. But that doesn't happen either, does it?
(No offense to whoever might be offended by this, it's just a selvish rant, portraying my views on this matter)