If instead of fucking around with putting MLK in jail for 30-60 days at a time, they've managed to get the laws changed so that organizing a sit-in was a felony, they could have kept him locked up, incommunicado or nearly so, for years and kept him on a tight leash (as a convicted felon) even if he got out.
The scarier people could either have gotten the message or been shot while resisting arrest.
We've got the necessary laws, 100 times over, by now. The protests that happen are ineffective because anything that threatens to become effective will be destroyed in no time.