Ok, so I'm actually gonna have to kinda-sorta agree with pessimizer here.
Black people are 13% of the population. They are not all poor, and only mostly under attack by the police. They certainly don't all agree with BLM, even if I personally do. This means BLM represents, generously, a good deal less than 10% of the population.
As to "Islamic terrorism", well, what Islamic terrorism? The most mature thing we can do is to admit that Islamic terorrism is mostly a European problem rather than an American one, and that homegrown mass shooters are a much larger problem, one which can easily be addressed by ameliorating or solving many of our other absolutely dreadful social problems.
So when you put BLM and Islamic terror together, how much of the population have you got in your coalition? 10%? Let's throw in LGBT for another ten. The most outspokenly neoliberal-feminist women. Uhhhh, maybe another 15? Millenials? How many millenials are there?
Except that your coalition strength in this "movement of movement" strategy is constantly being undermined by your own embrace of neoliberalism. Remember the whole #NotHereForTheBoys debacle? Feminists, LGBT people, black people, and Middle Eastern human-rights activists all need food to eat and a roof over their head, and neoliberalism keeps pushing the Professional Achievement Waterline necessary to have that basic standard of living higher and higher. You can't go around shaming people for supporting Bread and Peace and expect to have a coalition left. "I'm a queer black survivor, and I'm starting at Goldman Sachs next year!" is the most morally dishonest and repulsive platform I've ever seen, but it's exactly what Hillary ran on.
A workers' movement, on the other hand, represents that lovely fabled percentage we heard about in 2011: 99% of the population.
You want to see a Democratic Party that can work? It was called the Rent is Too Damned High Party.