I think it comes down to:
1) Singing songs as they were, in context. For example, in an historical program about previously accepted racism. Explaining the terms were common and acceptable will leave people asking why you didn't just change them to something relevant today in a typical concert,
2) Changing the offensive words so the words don't wind up being the audience's focus instead of the whole song.
3 Not singing the songs.

The people listening gets to make up their minds about how they feel about the songs, no matter whether the performer thinks they should or shouldn't be offended. You're probably going to piss somebody off -- just make sure it's worth it.