Unfounded assumption.
Progressives aren’t immune from this. In fact, it was a conversation about how to improve conditions inside Basecamp that led them to shut down this conversation. They couldn’t deal with the criticism and didn’t feel like they needed to worry about it.
Read White Fragility and hear someone who has actually led conversations about racism tell you how badly white people – including white people who have voluntarily attended a seminar on racism – have responded when faced with evidence that they, too, might need to work on their own racism.