Once violence is escalated different reactions need to be expected and countered appropriately to de-escalate. Its not defending womens honour, there are two highly unequal groups interacting here, which exposes the weak group (the couple) to greater risk of duress.

The cop escalated unpredictably and violently with little the others doing in the moments between to reduce that threat. The other implicitly gave their acceptance of this new level of violence and unpredictability in those fractional moments. Due to the disparity in power between the cops and the couple that escalation and those few moments become extremely dangerous.

The situation would have been very different if one of the other cops had checked the dog guy and told him to take a walk down the hall a few paces. Breaking that momentary rush of blood to the head is often all thats needed to halt severe forms of violence occuring.