The meek passivity with which the white Left has absorbed the aggressive entitlement of "black lives" wreckers harassing the Sanders campaign (the socialist has real-life counter-revolutionary wreckers, but he can't say it!) reveals a new stage in the ever-evolving Democratic coalition of the fringes.
Addicted to black outrage, the party is compelled to adopt an organizational model similar to the Mafia, where a dominant individual or "family" commands a percentage of all criminal activity in a given domain. The black faction (which is not to say black Democrats but everyone involved in black advocacy, including Soros the consilgiere manipulating a clueless, volatile godfather) is the crime boss and nothing goes down in the boss' territory without his approval--and nobody so much as sells a dime bag without the boss getting his taste. That's why you don't say "all lives matter"--you're cutting out the rightful originator of the grift.
Old Bernie was just getting the held-by-his-ankles-out-the-window treatment to remind him to whom he must "kick up".