It should either be sung uninterfered with, or not sung at all. There is no point in being mealy-mouthed about such things or in trying to impose contemporary values upon the cultural products of another time: that would be to tell deliberate lies about the past.

Personally, it's a song I don't feel able to sing; but I see no reason why it shouldn't be sung, with a sensible preamble explaining the context. It's potentially very educational, and by no means only in terms of the historic blood-libel involving the Jews: most minorities (and perceived "enemies") have had such stories told about them at one time or another, and it ought to make an excellent object-lesson in the dangers of accepting, unthinkingly, the "received wisdom" kind of prejudice which is still only too common throughout the world. I doubt if any culture is immune to it, and we all need reminding of that.