From their perspective, decisions made by Bernie are more likely to benefit you, black people have gotten and continue to get the empty promises with no face time, and the okey doke, from leaders way more often, and for far longer, and with a lot more at stake. It's a much bigger gamble, trust.
But I get what you mean, telling voters how they should vote is kinda the point of a campaign. It's why many blacks prefer to get that from other blacks. The imbalance of power is inherent from the start when a privileged person with historical advantage is having a conversation with a historically disadvantaged person, regardless of the topic. But that doesn't mean you can't present facts, policies, record, etc in non-persuasive ways and leave people to their decisions on their own. In my opinion, if it's obvious you care, they will see it. A lot of white Bernie supporters approach black voters as if they are white - big mistake. This is a perfect example of how teaching diversity in color blind terms does more harm than good, despite intentions.
The excerpt I posted is one small part of the article, there are many other good points. In hindsight, I should have made the excerpt about the concern if Bernie can take on the republican establishment, they want someone that can fight them and beat them soundly. Bernie doesn't play the slice and dice game so he has to inspire confidence that he can hold his own in the blood sport aspect of beltway politics. I know he can and we are a part of that, the people. We show up to have his back, it's how he will get things done. To be fair, blacks have no reason to feel confident that whites will show up for them. They may come to trust Bernie but everyone else? White Bernie supporters have to show that they will, and not as a temporary commitment.
Blacks understand better than anyone what a rigged system means, Bernie is a natural leader for us. We just have to overcome a lot of bullshit.