Sanders has long been fighting against the persecution of people of color in the US, even ending this speech in 1991 with a bold statement about how blacks are disproportionately punished by the country's criminal justice system.
While rival Hillary Clinton was a member of the Young Republicans in the 1960s, Sanders marched with Martin Luther King Jr. and took part in sit-in’s for equal rights. His fight has continued to this day.
"It is very important that we say the words 'black lives matter,'” Symone Sanders said in her speech before the candidate took the stage. "But it's also important to have people in political office who are going to turn those words into action. No candidate for president is going to fight harder for criminal justice reform and racial justice issues than Senator Bernie Sanders."
Earlier in the day, actress and comedian Sarah Silverman made a guest appearance at an event at which Sanders spoke in Oakland where he was formally endorsed by National Nurses United, the largest organization of US nurses with 185,000 members.
During the event, a nurse called in and asked Sanders how he would address racism within the criminal justice system.
"When we talk about creating a new America, at the top of our list is the end of racism in all its ugly forms," the senator said. "All of us were nauseated, when we have seen the videos… we know that if those folks were white they would not be dragged out of cars and thrown into jails."
"Senator, do black lives matter to you?" a woman in the crowd asked.
"Yes," Sanders replied.
Supporters are hopeful that answer will help assuage left-leaning activists’ concerns.