I've thought about this a lot and have come to a conclusion: This type of violence is normalized. It's expected at this point after centuries of it. From hanging, whipping, raping, poisoning, beating, to gunning down; white violence against black people is in a strange way, the status quo. (Side note: this is something explored in depth in a book called Post-Traumatic Slave Syndrome which I feel is necessary reading as much as the New Jim Crow).
This is considered normal while the reverse, black resistance to that oppression particularly the violently is considered an aberrance. It's "surprising" to society to see people who live under the thumb of all-encompassing and violent oppression fight back in kind. In essence, society never expected to be bitten back. The wealth of people in the Nazi-punching topic who are defending the Nazi see that violence as a shock and a complete upending of society while this as just another news story.