People with no self control shouldn't hold responsible positions. If your having a bad day you shouldn't be in a uniform dealing with people. Goes for any job, not just cops. Imagine if nurses behaved like this, punching every patient who pissed them off. Yet they get paid less than police for some reason.
I am not anti-police at all. Strongly disagree with the ACAB bullshit in Australia. Some cops are bastards for sure. I think they have a tough job and an important one even if their recruitment and discipline sucks (less so in Australia than the US but we could do better). I feel particularly sorry for the ones who get shot dealing with cookers and some of the stuff they have to see and deal with.
If the police service can't self discipline and weed out the trigger happy snowflakes then the public lose faith in them. They need to put cops like this on suspension and retraining. They might not have the right personality for this sort of work. It makes them look week. If your an agitator and want to start a riot it is so easy to bait weak minded law enforcement.
Ideally, if things are as clear cut as shown in the video. If the protestor committed some unseen offense like spitting on the officer it would certainly justify an arrest, something that might require force if resisted. This guy had his hands in the air. Hard to make any case that this response was justified in any way. Even the cops are innocent until proven guilty though so this is all just opinion.
Going in throwing punches makes it look like the police were drafted out of a particularly incompetent pub brawl. Weird behavior for trained public servants. I don't get how that is justified as crowd control. Makes the cops look terrified and pissing themselves with fear in a country where ordinary people take down armed terrorists with their bare hands and milk crates.
In my opinion this sort of behavior brings the service into disrepute and if not dealt with sends a message that violently assaulting peaceful protesters is tolerable. Training and recruitment have a cost and there could be systematic issues with culture and training that need to be addressed and dealing with individuals and not the organization and leadership would be short sighted. This should be investigated right up to Minns and the instructions he gave about the handling of the protest. NSW police have earned a bit of a reputation for being political enforcers.
To be fair to the cops there are protesters whose aim is to provoke a violent response from police by whatever means necessary. The police have no choice but to defend themselves and establish order with that crowd and people get hurt on both sides. There is a time and place where the police have to use violence to maintain order. In my opinion this didn't look to be such an occasion.