The institutions I'm talking about include slavery and Jim Crow. They had nothing whatsoever to do with justice and fairness, certainly not toward black people.
OTOH, criminal organizations are a beast of a different species. To think that a march, and media attention, would affect the 100 the same way is … rather naïve (IMHO).
The march was not meant to affect the 100. The march was meant to rally the community and build solidarity among them so that they wouldn't let themselves be rolled over by the 100 anymore, so they'd have the courage to fight back. It was a statement that the marchers intended to follow the example of heroes like LaWanda White and Black Lightning, that they would build on what those two had started.
Surely you've seen stories like that before -- businesses terrorized by a protection racket, a community leader rallying them to stand together and collectively refuse to pay, never mind the risk. I know I have; it's a pretty common fictional trope. Protection rackets thrive by making the business owners too afraid to defy them, too afraid to stand together and present a united front. If the victims of the racket decide to stand together against the racket, that isn't because they think they can reason with the racketeers, it's because they want to show the racketeers that they aren't afraid anymore, that even the threat of death won't keep them under control anymore.