How many failed protests and movements are enough to determine if the tactic works?

I feel like we’ve reached that point. Honestly we reached it a decade ago. The civil rights protests were largely nonviolent but didn’t really gain traction until they were counter pointed with actual violence from the same side. Justified violence. They have never and will never listen to our voices. Only just enough to get us calmly walking out the door with reassurances so they can change the locks again.