>my teammates always had something to say about everything. But when it came to the violent policing of black bodies, they were silent

Debate is probably the wrong term, seems he was just looking for an acknowledgement of the problem. After one of those police shooting incidents I came into work and all of my coworkers, all white and asian, were talking about how bad the incident was. People at work come together and talk about major traumatic news stories all the time. A consistent absence of that when it relates to a specific topic might seem....strange.