A difficult one MrrzY (are you really from Liverpool?)
Personally, I wouldn't sing a song where the racist content is malicious -As a singer - if it just reflected the language of the times I would change it so as to reflect my own language usage and also, so as not to give offence, especially in Britain and America, both of which have acute and accelerating racism problems
My grandfather sailed before sail and remembered a few shanties from those days (his son, my uncle Jerry, once sang them to a crowd of folkies at Whitby)
One of the shanties was 'Johnny Comes Down from Hilo, which had the verse;

"I've never seen the like since I was born
As a big buck n..... with his sea-boots on"

I heard it sung at home like that, yet our family was fanatically anti racict - my grandmother was arrested for hitting Mosly with a stone at a Blackshirt rally in Liverpool
If I'd have uttered a word of racicm like that I heard in school I'd have been flung out on my arse

If you decide to sing blues, any of the black singers used the term unselfconciously - we wouldn't get away with it, nor should we

I have a song we recorded from Irish Travellers which contains the term "nacker" - a deeply offensive racist term when used by buffers such as us
I want to learn it - what do I do ?
I'll almost certainly change the term to 'Traveller' or 'Tinker'
These old songs have survive as long as they have because the singers have constantly adapted them to suit the times
We no longer have an oral tradition but there's no reason not to change the songs
As a researcher the song would remain as we found it - probably with an accompanying note
Jim
Our song, from Mary Delaney, Blid Travelling woman

Mary Delaney sings Donnelly
There was a jolly knacker* and he had a jolly ass,
And he stuffed his box of pepper up the jolly asses arse.
Oh then, “Brave done Donnelly, good enough,” says she,
Oh then, “Well done Donnelly, and you're my man,” says she.

There was an old woman in the corner over eighty years or more.
And, “For God Almighty's sake”, she says, “will you solder my old po?”
Oh then, “Well done Donnelly, good enough”, says she.
Oh then, “Well done Donnelly, and you’re my man”, says she.

I soldered in the kitchen and I soldered in the hall,
And when I finished soldering I done the ladies and all.
Oh then, “Brave ould Donnelly, good enough”, says she.
Oh then, “Brave ould Donnelly, and you’re my man”, says she.

She sent me up the stairs for to dress the tinker’s bed,
The jolly knacker followed after me and tripped me on the leg.
Oh then, “Well done Donnelly, good enough”, says she.
Oh then, “Well done Donnelly, and you’re my man”, says she.

If you’re an honest woman as I took you for to be,
You’d have a basket on your arm and a kid belonging to me,
Oh then, “Well done Donnelly, good enough”, says she.
Oh then, “Well done Donnelly, and you’re my man”, says she.

I am a jolly tinker oh, for ninety years or more;
And a divil a finer job, me lad, I never done before.
Oh then, “Brave ould Donnelly, g’out that sir”, said she.
Oh then, “Well done Donnelly, and you’re my man”, said she.

* knacker: originally a horse for slaughter but also used for tinsmith; often now a general word for traveller.