To all with regards to offensive Songs.
This is taken out of a Song book "Let's Sing Manual" obtained from the The Girl Guides Association New Zealand Inc. which I believe best answers the problem of a song which may "give offence" and written by Mary Chater, the then Music Adviser to the U.K. Girl Guides Association:
"I suggest that the best and most complete solution is to know and explain the background of the song rather than to ban it everywhere for always. In certain company one would not use a tune with a very strong unpopular association. But there are many other groups who would appreciate the origin of a song if it was explained. This is a plea for more filling in of background. It is up to those who know the history of a song to pass the knowledge on to others."
I think this is the best explanation I have heard to date, and the Song Book "Lets Sing Manual" has a lot of background info on songs and I recommend the Book.