Because maybe it won't be divisive if people know the facts and the context of it. Or maybe it still will be.
I haven't seen any of our athletes say: 'I'm offended because it was first performed at a minstrel show'. (I could have just missed it, and I could certainly understand if they were).
I have heard two people say they are offended because the think the song refers to, or is adapted from a song, warning slaves that the eyes of their masters are upon them and they can't ever escape. I don't think that is anywhere close to factual.
Some could still be offended by the association to a minstrel show- but there is a large degree of difference, to me, if our school song was intended to warn/intimidate slaves vs being first performed at an event I find egregious.
I find the fact that we HAD a minstrel show more offensive than any songs that were performed there. It would not surprise me to learn they said the Pledge of Allegiance, sang the Star Spangled Banner, said a group prayer, or were served tea at the same event. I would find none of those things offensive on their own based on their inclusion in the show. The show itself, now that I find offensive.