Let me get this straight.
The song was written to celebrate the end of slavery.
it was a favourite song of civil rights campaigners.
It's obviously a bittersweet but upbeat tune (or will I offend people by saying that, too).
It encourages the crowd. It says nothing horrible (directly).
But some people assume it's a song about slavery being an ok condition.
So because SOME people totally misunderstand the song, it might be offensive to sing.
Neah, I give up. All logic lost.