I think Bernie Sanders understands that tackling racial equality is about as effective as fighting terrorism. They're abstract concepts that can't really be approached with a policy that will be effective in their goals.
The fact of the matter is, black people make up a disproportionate amount of poverty in America. The answer to helping black people is not posting #blacklivesmatter and trying to take down the Confederate flag from monuments. The answer is decriminalizing drugs, addressing income inequality which absolutely favors the rich (predominantly white men) while disadvantaging the poor (predominantly black men/women), and fixing systems that are currently broken.
Talking about race is all well and good, because it sheds light on issues that many would otherwise not know exist, but that's about all the good crying over race does. You have to look at what affects and hurts racial minorities, and address those issues, not some undefined "race issue".