> If you are mad at somebody at work and you hit them a little bit that is egregious and completely unacceptable behavior

The difference is that under no circumstances does an office job require violent interaction where as for a police officer, their job does sometimes require violent interaction. And in that sense, what these officers did is even worse and should be punished worse than if an office worker used the same violence: we empower police officers to use violence to intervene when necessary. We give them weapons and leeway to use force. To take advantage of that power could arguably be considered worse that if a civilian does it.