It's hard to imagine a one-size-fits-all solution to this problem, because:
- almost no authors would countenance major changes to a book without their input and consent
- many authors would be okay with minor changes if it would go over better with readers or increase sales
- the rights of the majority of books by dead authors are not held by people who can be relied upon to make informed, public-spirited decisions
Take Agatha Christie: a lot of her books, in audio editions, omit racial slurs and denigrating language.
Lord Edgware Dies, say, has a bit at the beginning where Poirot prophesies trouble for a young actress, because, as a Jewess, she will obviously have trouble controlling her love of money. The modern audiobook edits this passage so he just mentions the love of money generically and her ancestry is never mentioned.
Frankly, I think this is an improvement? The bit about her being Jewish doesn't add much to the book, and it's
much easier to listen to enjoyably.
(That's actually an interesting wrinkle, because the edits are only present in the audio version; the print and epub version match the original British text. That makes sense, in a way, because books with problematic content can be read privately, whereas if I'm listening to an audiobook with racial slurs in it I may be uncomfortable listening to it in public.)
There's a much sillier edit in
Hickory Dickory Dock, where a serious black student named Elizabeth is nicknamed "Black Bess" by the other students at her boarding house. The text mentions that she doesn't mind because she knows it's an affectionate gesture and not meant to be hurtful. The audiobook changes the nickname to just "Bess", but keeps in the bit about how she doesn't mind even though there's no longer anything there for her
to mind.
There are authors who would mind this and authors who wouldn't. I'm sure J. K. Rowling would be incensed if anybody tried to edit her books to make them less <insert all the various reasons people are mad at J. K. Rowling>, but I doubt Christie would care. I mean, she wasn't making high art and I can't imagine she had a big enough bee in her bonnet about The Jews to insist on keeping a derogatory reference if it would hurt sales.
Unfortunately, Christie is dead and the decision won't be made by her, but by publishers, who are only thinking of the bottom line and not about the needs of art or about a work's potential to hurt.
The moral of the story is that copyright should last for death + 10.