Recently I happened to re-read Mark Twain’s Adventures of Tom Sawyer and was struck by Twain’s treatment of Red Injun Joe. I had always thought of Twain as a humanist, one who had sympathy for enslaved African Americans and even Africans in Belgian Congo.
Not only does Twain contemptuously refer to Injun Joe as a ‘murderin' half-breed’, but also shows him as a ‘stony-hearted liar’, someone inherently back-stabbing, cowardly and hell-bent on revenge. When Huck Finn finally tells the Welshman that the deaf and dumb Spaniard is actually Injun Joe, the Welshman responds thus: "It's all plain enough, now. When you talked about notching ears and slitting noses I judged that that was your own embellishment, because white men don't take that sort of revenge. But an Injun! That's a different matter altogether."
Here’s a more detailed inspection of Twain’s attitude towards native Americans.