So, Mark Twain stays in the news even 100 years after his death. First, with the initial volume of his Autobiography, finally published in the form planned by the author. Second, with the controversy stirred up by a "new" edition of Adventures of Tom Sawyer and Huckleberry Finn in which the offensive racial epithets "injun" and "nigger" are replaced by "Indian" and "slave" respectively.

Undoubtedly the use of the word "nigger" – surely the most inflammatory word in the English language – makes Huckleberry Finn a tricky novel to teach. The book has recently repeatedly been judged as unsuitable for schoolchildren to study in the US educational system – and one can fully understand the feelings of anger and humiliation that many African American children and parents feel at having such a word repeatedly spoken in the classroom (the word appears 219 times in Twain's book).

But that is not necessarily a reason for replacing it with a gentler (bowdlerised) term. Twain was undoubtedly anti-racist. Friends with African American educator Booker T Washington, he co-chaired the 1906 Silver Jubilee fundraiser at Carnegie Hall for the Tuskegee Institute – a school run by Washington in Alabama to further "the intellectual and moral and religious life of the [African American] people". He also personally helped fund one of Yale Law School's first African American students, explaining: "We have ground the manhood out of them [African Americans], and the shame is ours, not theirs, and we should pay for it." And his repeated use of that derogatory term in Huckleberry Finn is absolutely deliberate, ringing with irony. When Huck's father, poor and drunken white trash by any standard, learns that "a free nigger ... from Ohio; a mulatter, most as white as a white man ... a p'fessor in a college" is allowed to vote, he reports: "Well, that let me out ... I says I'll never vote agin ... [A]nd the country may rot for all me." It is very clear here whose racial side Twain is on. Similarly when Aunt Sally asks if anyone was hurt in a reported riverboat explosion, and Huck himself answers "No'm. Killed a nigger," she replies, "Well, it's lucky; because sometimes people do get hurt." The whole force of the passage lies in casual acceptance of the African American's dehumanised status, even by Huck, whose socially-inherited language and way of thinking stands firm despite all he has learnt in his journey down-river of the humanity, warmth and affection of the escaped slave Jim – the person who truly acts as a father to him.

Language counts here. As Twain himself said: "The difference between the almost right word and the right word is really a large matter – it's the difference between the lightning bug and the lightning." I respect the motivation of Alan Gribben, the senior Twain scholar who is responsible for the new edition, and who wishes to bring the book back into easy classroom use, believing "that a significant number of school teachers, college instructors, and general readers will welcome the option of an edition of Twain's ... novels that spares the reader from a racial slur that never seems to lose its vitriol."

But it's exactly that vitriol and its unacceptable nature that Twain intended to capture in the book as it stands. Perhaps this is not a book for younger readers. Perhaps it is a book that needs careful handling by teachers at high school and even university level as they put it in its larger discursive context, explain how the irony works, and the enormous harm that racist language can do. But to tamper with the author's words because of the sensibilities of present-day readers is unacceptable. The minute you do this, the minute this stops being the book that Twain wrote.

• Peter Messent is the author of the Cambridge Introduction to Mark Twain