I don't think Sanders is a single candidate issue. He does beat to death his positions on the 5 or so issues he's staking his candidacy around: income inequality, campaign finance reform, and what amounts to a huge expansion of entitlements (health care/education). Ok, so that's really just 3 things when you boil it down.
Does his laser focus on those things turn off African Americans who are justifiably concerned about a police state gone shitballs insane? (Thanks, black man in the White House. Kidding. Not kidding. Only sort of just barely kidding.) Yeah, probably. My thing, though, is that the people who are saying, "Well, what about Hillary?" have a legit point, at least as far as I'm concerned. If she wants to run in part on Bill's record in the 90's (and let's not pretend she doesn't) then his record on welfare and police expansion should absolutely be up for debate. Maybe shitting out 100k new, poorly trained cops onto the street was a poor fucking idea, it turns out. To say nothing of her taking money from private prison corps (I know, she stopped, but it's still a legit criticism imo)
Basically, my problems with Hillary are that I feel there are a lot of legit gripes to be had with her. The sad thing is that not a lot of people (hello, Killer Mike) seem able to bring those criticisms to bear without falling into the easy and stupid trap of couching them in sexist terms.
Ultimately, though, like I said above: I will gladly vote for Hillary over any lunatic the Republicans nominate. And it will be a lunatic, most likely Trump at this point IMO.