This right here strikes pretty close to the crux of the problem, apart from the daily, generally partisan, bullshit, and highlights exactly how deeply-rooted and systemic these problems are.
The public perception and expectation of law enforcement is not consistent with what law enforcement is, nor what law enforcement does, in the context of Western justice systems. In fact, it's the complete opposite of what that perception and expectation is. And no, this isn't about systemic racism, training methods, the dubious origins of contemporary police forces, what personality types the job attracts, or any other discrete issue within the broader context.
Pay close attention to this video, starting at 26:48:
That's a cop, explaining to a group of law students, exactly what his job as a cop is and how that contrasts to how the justice system nominally operates.
Here's the TLDR: cops don't act on the presumption of innocence. Their job as state actors is to aid prosecution, and they do this through investigation, case-building, arrest, detention, and interrogation such that prosecution is best-informed as to how to exercise its prosecutorial discretion, and should a case go to trial, maximize the possibility of conviction. Thus, cops actually act on the presumption of guilt in order to most effectively aid prosecution.
This "protect and serve" stuff is public relations bullshit. Maybe once in an entire cop's career, if they're lucky, they might have to act swiftly and decisively to do something that might make someone a teeny, tiny bit safer. And guess what, that isn't engaging in high speed chases, gunfights, busting up "violent" protest, or any of this other dumb cop TV (news or fiction, not that there's much difference) bullshit the American public is awash with on a daily basis. In almost every case, that shit endangers public safety more than it provides.
And the shit cops could do to foster public safety? They either don't do it, or fuck it up.
Because that's not cops' jobs. Cops' jobs are to act as prosecutorial field agents.