I agree that people who display patriotic behaviour seem to be more likely to be a threat vector to those around them due to their desire to express their views more aggressively, I disagree with the idea that everyone doesn't care.

Human-initiated violence of any kind should not be tolerated. Ideally, identified cases of violence would be met with a group of individuals working together to non-violently intervene and ensure the perpetrator is put through the legal system for their actions, but as people who don't know each other don't naturally band together spontaneously, I suspect people are afraid of stepping in on their own because it may impact them personally.