The copper ought to have an extremely hard time in court justifying his actions. He is supposed to be trained how to act and react in this kind of situation. He's not supposed to be your average thug who sees red and lashes out. Yet, that is what he did.
The victim was passive and not approaching or goading the police.
If the police, as is claimed, thought he was obstructing them, then there is a better way to deal with the situation.
If the police shouted to him and he did not hear, or ignored them, then they could have come round in front of him so he could see them and asked him to move away. Had he declined, they could have moved him on without the need for any violence.
The shove was entirely uncalled for.
I don't honestly know how anyone who has seen the video can come to any other conclusion.
Given the copper's previous, this is his MO. He is not fit to wear a uniform.