> But they weren't protesting the proprietors of those businesses for complying with the law.
Yes, they were. The Greensboro sit-ins began at Woolworth stores because they had explicit policies that went above and beyond those required by Jim Crow laws. They even sent a letter to Woolworth’s, not the state[1].
Edit: And, you’ll note: the Greensboro sit-ins didn’t provoke asymmetric police retaliation. What the students did wasn’t even illegal, it was merely against Woolworth’s store policies.