Black Lives Matter tactics are making things worse, not better, on a national level. Police execution of African-Americans is a terror tactic. The inability of those who oppose terror to do anything about it can serve both to magnify fear and highlight the weakness of its opponents.
For the first half of the twentieth century lynching was the terror tool of choice. African-Americans were burned alive in America. The NAACP fought for a federal anti-lynching law for over thirty years. America still has no direct federal anti-lynching law. (Wikipedia) One of the reasons for this is that failure of a federal law served to amplify the terror. Black people were being burned alive in America and all the opponents of lynching could do was argue that if a law was passed maybe something could be done about it! For white Southerners the message was clear. Those who supported change were weak and dangerous. For the love of god how can you do nothing while your fellow citizens are being burned alive. If the political choice is between the weak party that will do nothing and the strong party that is killing people, many of those not in the target group will go with the strong party. Who knows what they will do to you if you vote the weak party, which clearly cannot protect its supporters.
Southern racists knew that the Posse Comitatus meant that the federal government had no effective way to intervene. The heavily Southern officer corp of the US military also knew what was and was not a legal order. And this continued until Eisenhower sent the 101st Airborne into Little Rock and the racists confronted a power greater than themselves. Then everything became possible. Racists would spend the next sixty five years looking for some way to weaken the government to destroy the force that proved greater than hatred.
Which brings me to this quote from Trump on Politico:
But no one takes the stage at a Trump rally without Trump’s say-so. Asked in Michigan about the Black Lives Matter protestors who had seized the microphone at a Bernie Sanders mega-rally in Seattle, Trump said there were differences between him and Sanders, and similarities, too. “That will never happen with me,” he said. “I don’t know if I’ll do the fighting myself, or if other people will. It was a disgrace. I felt badly for him, but it showed that he was weak. You know what? He’s getting the biggest crowds, and we’re getting the biggest crowds. We’re the ones getting the crowds. But that’s never going to happen to Trump.” First, I apologize for bringing in the Democratic primary. I think the quote makes a point. We do not live in a well function Democracy. In a well functioning Democracy protests in the streets with the simple demand "stop killing us" should garner immediate action. Instead we live in what is increasingly becoming a proto-fascist state where concepts of power and weakness are central. How can progressive help you? We do not control the House. We do not control the Senate. We do not control the Supreme Court. Our faction of the Democratic Party doesn't control the Presidency and Obama is unwilling to be seen a weak by calling for Civil Rights reforms that are not going to pass.By protesting that progressives do something, you highlight that we lack the power to do so. This shows us as weak. In a political system that turns on weakness and strength many voters will either not vote or support the strong party. After all, your protests are proof that the weak party cannot protect its supporters. In such a situation voters are more likely to go with the strong party in a "kill me last" strategy than support the party that won't protect them, making themselves targets.
This is not say shit down and shut up. Protests can work to change the local political scene. I'm not even going to say not to protest in front of Democratic candidates. Simply don't do so in a way that makes the candidate look weak. Even if that candidate loses, the perceived weakness attached to the party as a whole. Winning a primary doesn't do you much good if you sacrifice your general election chances to do so. (And I'm sorry to say, looking at some of the most recent polls, I'm not convinced that Trump is doing so).
Successful Civil Rights protest requires that you expose the racists as powerless. Figure out some way to get on TV protesting Trump and his ilk. For all the frustration that #BLM feels about the lack of progress on police violence I can only say this: this country is deeply broken and if you fight this fight assuming that the country will react like it should then you are likely to be worse off at the end of it.