I think the the hatred of Copmala from the progressive wing of the party is quite real. Kamala's history as a DA is not seen as a positive. Given the disproportionate damage the criminal justice system does to black communities, I'm sure much of that distaste is very real. The "tough on crime" democrat is a bit of an outdated political model.
That's the far left, not the average black person who has to worry about their kids, grandkids, nieces, nephews, and so forth getting gunned down - which is why they're the ones organizing against violence whenever and wherever they can. What they don't want is police running around beating random people, and then refusing to investigate actual crimes - or worse, a Ferguson-style white supremacist shakedown PD.
Harris has the same basic problem almost everyone else does - Biden is strongly connected to Obama, and a lot of people have the Obamas photo next to MLK Jr. and Jesus on their mantle. College-age black people, meanwhile, are still leaning towards Sanders as far as I can tell. There's a fairly strong Harris movement, with Warren in 4th.
Again, there are things I like about several candidates - including a few who poll well below her. Overall, I'd probably go with Warren, mostly because she's the only person to say much of anything about the radicalized McConnell courts (By which I mean "Let's toss out Roe v. Wade, quite possibly Brown v. Board, and not let congress delegate authority to experts in the EPA.") But I find the loudly negative coverage of Harris, this early in, to be bizarre.
It's not as vital in the primaries outside of a few Southern states like SC.
It'll be the *entire* South. And last I saw, he was getting killed in Nevada as well - picked specifically to increase the influence of Hispanic voters in early primaries. Hillary was actually pretty vulnerable in 2016, but when the Sanders campaign went down this path, Super Tuesday ended his bid in all but theory.