Two things being true does not make one thing less true. Every economic messenger does not need to be versed in every progressive issue. But if you want to eventually become a serious contender and not a way to just generate mid level support for the party as a whole, then Bernie needs to address each of the multitude of progressive activists issues. BLM, issues about fair pay for men and women, the corrupt and corporate run correctional system that has become a second slave state, the mis-appropriation of the war on drugs, a global economy vs failing us cities, etc. Each of the groups in these arenas have more in common that what separates them.
So we need to figure out a way to stop fighting over how we are different and focus on how we are the same. As a Black man who is not yet been killed by the police or suckered into the legal shell game of incarceration slave labor, maybe I am missing something. I don't have any skin in the game (although my skin is black and I do have a life). But I am also cis gendered and care about the rights of people who identify differently than I do. I have a stable, yet unsettling job, but certainly care about the economic disparity that exists, and so on. None of us is One Thing or can live in a world where we only care about one thing. Because if we do that, our One Thing will become almost important and end up as nothing.