If your automatic response to assault is a kick in the head that’s on you, but I’ve defended myself against violent people and not resorted to kicking them in the head and turning “homicidal”. If you have such poor control over your emotions and reactions you shouldn’t be a police officer. It’s unsafe.
This isn’t some lone woman or even man walking down the street at night doing everything they can do defend themselves against a random attack and getting understandably carried away.
The police officer who was assaulted had back-up and support in their fellow officers and the person was now lying on the floor, so were not such an immediate risk that they needed to have their heads kicked.