I don't believe there's any such thing as peaceful protest.
According to some magickal/philosophical worldviews, any attempt to enforce one's own will on another- even in the interest of justice or self-defence- is an act of violence. At the core of even the most nonviolent protest is the basic message we oppose you, and there are many of us. Regardless of the intent, facing down a large group of angry people touches on primal fight or flight responses. It makes no difference whether you're brandishing weapons or words, as this is a base level, lizard-brain threat: there are too many of us for you to control. You are outnumbered. You will suffer if you engage. Even in the most gentle and respectful of democracies, with the most noble of motives, protest sends the message: listen to us or we will vote you out of office. The action may be more civilized, but the underlying psychology is the same.
The reason people like Gandhi were successful is because of the volatility of the situation which surrounds them. MLK wasn't just a leader- He was the "good cop" to the Black Panthers' "bad cop". Against the backdrop of riots and armed protests, his presence allowed people to say you can deal with the calm and rational minister or the angry black men with the guns, but one way or another this is getting settled.
We don't need a calm and peaceful crowd- We need a calm and peaceful PERSON standing between the authorities and an angry mob ready, willing, and able to massacre every cop, judge, and elected official in the county- And we need that person to stand up and say you can deal with me, or you can deal with them, but one way or another this is getting fixed today. We need that person to be someone the angry mob trusts enough that they will put down their torches and pitchforks just long enough to say we will give you this one last chance to make things right.
Then we need to talk about the militarization of police. We need to talk about the racial makeup of the police and the city council. We need to talk about poverty and education and building communities. We need to talk about the uncomfortable fact that the tragedy here wasn't the shooting of an unarmed teenager, but the 50 and 100 years that led up to it. Not the fact that it happened, but the fact that our society is so broken that this kind of thing just happens.
We need to have that conversation, but we are the kind of species that won't- Not until we are facing down an angry mob ready to show us that we have no choice.