There's a perfectly legitimate argument that as cops have the ability to use deadly force, there's a lot of good reasons for the public to want their work to be scrutinized heavily, but it's also perfectly understandable why police aren't super fond of it.
I feel that in many ways the police handle a range of responsibilities more serious to citizen health than handling some level of classified government information.
Only in the sense that people aren't super fond of doing their job right.
Additionally, monitoring can also be exonerating if you are confident in the justice system, so I don't buy this idea that cops are uniformly against monitoring.
My point is that police officers, like you, find having someone staring over their shoulder while they work uncomfortable. So the fact that they don't like it and tend to oppose it doesn't mean they're inherently desiring to be corrupt or violent or bad cops.
And yes, it's definitely true that police are regularly accused of lying, and can find appealing having recorded proof of their interactions. There's a lot of extra rules and regs around body cams and when they have to be recorded, and how they can be used by the department that can make the issue cloudier.
But that fact is the seed that causes such corruption.
I hate to break it to you, but in any half-decently-ran company with an IT department, everything you do on your work computer, including reading this post, is monitored and recorded.
(And no, I don't exempt myself from anything everyone else is subject to.)
I agree on the accountability front - some agency somewhere needs to keep a comprehensive record of all of these 'black budget' 'operational secrecy' kind of things. Otherwise (as evidenced by the runaway CIA/NSA), having the option of secrecy becomes too alluring and therefore the norm.
At this point American citizens have pretty much zero idea what these agencies are doing on a daily basis - it's nice to believe they operate with our best interests in mind, but if not, how would we ever know?