It was only 20 years before the novel's publication that the Ku Klux Klan was formed, the Civil War ended, and slavery was abolished. Therefore, racism was still a common practice at the time; the civil rights movement didn't even begin some 70 years after the novel's publication. Mark Twain may have written the novel with the hope that it would be anti-slavery and anti-racist, but that doesn't mean he approached the topics very well.