Not an easy question to answer, because it is hard to find unbiased reporting or studies on it.
@tim has given a good answer, I would like to add a different perspective:
When you check not the media, whose main interest is the generation of headlines, but the extremist groups whose main interest is self-defense against the police, you find that both left and right consider the police their enemy. I don't think I need to detail what the Antifa thinks about cops. But I have as well seen pamphlets circulating in right-wing circles with advise on how to act when police arrest or question you, and I could re-print them with minimal changes and give them to Antifa activists and they'd think their people wrote those.
If both the left- and right-wing outliers consider the police to be on the other side, then it follows that the police is on neither extreme. Which stands to reason given that "the police" is a rather large force with many different people in it.
Looking at the political spectrum and what the terms stand for, it's clear that "law and order" are more naturally associated with the right, so it is no surprise that studies find policemen more right leaning. That does not necessarily translate to right-wing opinions on questions such as immigration, employee laws, economic principles, healthcare, etc. etc.
The clashes you see are most easily explained by viewing the police as the defenders of the status quo and the current politics of the country, no matter what that is. When left-wing activists protest for better social support, they will clash with the police. When right-wing activists protest against immigration, they will clash with the police. And when Corona-tired conspiracy theorists protest the lockdown, they will clash with the police. Heck, if lunatics were to protest against the government keeping aliens from Jupiter prisoner in their secret vaults, they would clash with the police - and that doesn't mean the police is pro-imprisoning-aliens.