Most of the songs I have come across w/ the "N" word have been originated by blacks- mostly in the slave days- includes spirituals, hoedowns, lullabies. Most of the of the other potentially objectionable songs (i.e. Stephen Foster) seem to be much more euphemistic and we get terms like "Darkie". The "N" word is basically just a dialect variation of Negro which still seems to be semi politically correct when compared to the "N" version.
As to whether or not to banish these songs, well I guess that would be a shame. They are historical and describe life as it was in the time period. It's unfortunate that Slavery, discrimination, all of the atrocities against people of other races have occurred, however, I think by keeping these songs alive it serves as a reminder and that no one wants to go back there again.
Just my 2 cents worth Laura