The irony of this whole issue is that by changing songs instead of keeping them intact, the ability to use that song as an illustration how people thought is diminished.
History is useful when it reports what really was, not what we wished was, and shunning the truth of the past, especially our recent past, encourages us to shun the truth of our present.
The Foster songs are a great example of sensitivity, extreme talent and blindness to a great wrong in the same individual. It shows to what degree we tend to accept the culture we are raised in as essentially correct, and, if properly taught provides a cautionary object lesson to examine such contradictions in one's self.