Albert, the above almost sounds as if you maintain that no injustice was done to black musicians in terms of status, recognition, and salary--it was just market factors. I find it hard to believe that you actually think this. A salary imbalance is a salary imbalance--white and black should be paid equally and treated equally. They were not.
The story is very familiar, and the facts basic--too basic to have to reiterate here. Who benefited? Well, who made the money? The music industry as a whole did--mostly whites, and not blacks who were virtually excluded from this. Who were the victims? You know the answer I will give.
If you admit that injustice was done (which I think you must), of what sort? If you can have collective or corporate injustice (which I think you must admit is possible), I don't think there is a problem with the concept of collective stealing. That and many other injustices intertwined with one another were committed.