Note that there were quite significant peaceful and good natured anti-monarchy protests over the weekend, and the vast majority of those taking part weren't arrested. So, we're obviously not talking about some widespread systematic crackdown on protest at this stage, but rather what appears to be a very bad call on the part of (some?) Met officers. At this stage it's too early to know why these individuals ended up being arrested, but it seems to me like some officers on the ground hugely overstepped the mark and I hope the arrested parties get a good settlement out of it.
However. There is clearly wider context that makes having a fair discussion about this difficult.
On the side against the police and government, there have been far too many instances in the past few years of bad calls, misconduct and, in some cases, using the position of authority to sexually abuse or murder women. There have also been reports finding evidence of systemic racism, homophobia and misogyny within the Met. These do not appear to be isolated incidents. It would appear the Met has a serious cultural problem, and the new Met police chief has admitted this is the case. There hasn't been any real discussion on whether authoritarianism is a factor, but police officers are bound to lean towards authoritarianism and would imagine that's makes them likely to abuse their power. On top of that, this recent police powers bill has been rushed through and hasn't been scrutinised as much as it probably would have been if they weren't working to the deadline of the coronation.
On the other hand, there have been a lot of disruptive protests lately causing, I think it is fair to say, a level of havoc that is not considered by most British people to be a protected form of protest. The Just Stop Oil, Animal Rebellion and Extinction Rebellion protests in particular have illegal disruption as an explicit goal. They have been blocking roads, gluing themselves to trains, throwing paint over art at galleries and have publicly stated they have plans to step up the disruption. The majority of Brits do not support this form of protest and have been demanding the police crack down on them, and I suspect there would have been a huge level of criticism against the police if they had allowed one of these groups to disrupt the coronation. Demonstrations and organised marches aren't controversial, but few people consider these new disruptive tactics to be a legal expression of protest. The other thing to consider is despite the recent issues, the UK is one of the countries where you are least likely to experience any sort of police brutality or corruption, and despite the coronation being controversial and attended by many thousands, only 52 people were arrested over the weekend, which is pretty good going for such a major event.
Personally, I'm sympathetic to these protest movements and agree with their goals, but we need to have a limit to what we consider protected protest. If they still want to take part in illegal protest and risk prosecution for political purposes, that is entirely up to them to decide whether their cause is worth that. But obviously we need to make sure the crack down on those sorts of groups doesn't spill over into limiting free expression as it has done here, and any police officer with these kind of authoritarian tendencies ought to be screened out of the police.