I’m a fan of the 4th Century Bishop, Gregory of Nyssa, who made one of the earliest (if not the earliest) known unequivocal condemnations of slavery as inherently wrong.
I’d say Jesus is the best example. He was WAY ahead of his time. Still is.
Another would be the original Buddha (Gaotama), but since he was a spoiled prince and Jesus was just the son of a carpenter, I’ll give the award to the J-man.
Leibnitz was pretty cool too, but not quite on the same level.
His plays Woychek (the basis for the libretto of 20th century classic opera Wozzeck) and Spring’s Awakening are mindboggingly discongruent with his time’s intellectual consideration of, let alone artistic encapsulation, of sexual and social “deviancy” and their wretched possibilities.