I don’t think they should edit words (eg., “nigger”) in “Huckleberry Finn” at all. The novel was written during a time when that word was in common usage——whether it was derogatory or not at that time, it reflects the mindset/culture/tradition of that era. When people read it today, they have the opportunity to look back and question and evaluate the “culture of ignorance” that existed back then (if you can call it ignorance, if it was part of common usage). In other words, today’s readers have a chance to sit back and think “Wow, people used that word everyday. See how times have changed. I’m glad times have changed.” If you take that word or other “derogatory” words out of that novel, people today lose the opportunity to reflect on that era and make constructive criticism. We learn from history and the “mistakes” people made in the past.
It’s sort of like taking an antique jewelry piece that was made in the 1800s and making modifications to it to “improve” its look. You lose a piece of history——how things were done back then, however flawed, just to make it look better. But leaving the antique jewelry piece alone, we can appreciate its “flaws” and how things were done back then.