Like Crookedbook, there were language boundaries set in our household when I was young. Butt was bad, and when we were to let our parents know what we needed to do to relieve ourselves, numbers were used in place of words. So in raising my children, I've drawn up a less stringent set of rules. The ones I adhered to were confining.(No smacking or slurping by accident at the table and absolutely no borderline words).
Now, I would by a book with the word butt in it. Yes. On the other side, I didn't buy the book about Walter the dog.
If it's done well, where it's not for the sake of using the word, but enhancing the story as only that one word could do, then I'm on the side of those who are good with it.