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.
If I were in this person's position, silence would make me feel a little weird. My coworkers actively deriding the protest that I'm about to go join would make me feel a lot more weird.
I don't think people are lying when they say that tech employees have their own biases and blind spots, and it doesn't necessarily surprise me to learn that race is one of them.