I'm not sure what the best song about racial equality is. But here's a song about everybody talking about racial equality.
I don't post in this forum, but this really isn't controversial so... ¯\_(ツ)_/¯ Just chiming in that En Vogue's Free Your Mind belongs here.
War by Bob Marley is probably a better advocate for racial equality. Of course, you'd have to give an assist to the author of the original speech, Haile Selassie aka Jah Rastafari.