It's easy enough to change lyrics to sound right and also become non-offensive to most people. "Sailor" conveniently has the same number of syllables as the n-word, and will scan fine anywhere. I've actually never heard "Johnny Come Down To Hilo" with line line qupted above; I've heard it as "an Arkansas farmer with his sea boots on." Now that MIGHT offend some Arkansas farmers, but not very likely--it simply points out the incongruity of a farmer wearing seaboots. The nature of chanteys is to change the words anyway.