I rather assume that the whalefish forebitter would have been sung both ways, according, maybe, to how much of a bastard the captain was.

..........................

So far as the other stuff goes, it strikes me there are three sorts of reasons that people go changing the words.

The first is to do with the fact that words change meanings, and that words that at one time were neutral can take on a different connotation, so that using them gives a false impression of what the song is saying.

The second is to do with not wishing needlessly to offend people who might take a particular expression as intended to hurt, because it often has been used with that intention.

And the third one is different, it's to do with trying to pretty up the past, and pretend that it was better than it was - so a song involving slavery might be prettied up to suggest it was about something else entirely. Or you get those modern TV Westerns where the black characters sail through being everyone's best buddies, and never running up against any problems of that sort, because there aren't any racists around. Which would have been great, but it wasn't so.

The first two can make a lot of sense. The third is to my mind very unfortunate.

But objecting to a change like "massa" to "master " seems a bit silly to me. That's just the same word, spelt two ways.