I am not blind to cases of bad practice by the police but I am not naive enough to think those cases define a whole police service.
The problem is simple and in no way at all limited to cycling*. The media and worryingly more recently, the public too, absolutely love to spin stories based on police corruption and police incompetence. Stories about police simply doing their job, or doing a good job however never get written about.
I have dealt with far too many cyclist RTCs in my service to recount, ranging from damage onlys all the way up to fatals, and I have had no complaints - I've also never had any acknowledgment of 'a good job' (nor felt I needed one btw). My jobs didn't make the papers (except the fatals), and they weren't held up there as an example of how the police work. On many of these jobs, the evidential requirements of our justice system meant we didn't get the result we wanted.
Spread it out further and my colleagues on shift have dealt with just as many (there used to be 50 on our shift, it's now fallen to 25) and in all those jobs, I know of only one where the cyclist wasn't happy and made a complaint - he said he was going to the local paper but I never saw the story. The complaint came to nothing.
"The police" as a whole are not useless. We are sometimes restricted by the rules we have to follow, and by the heavy evidential requirements of our system. There are, and anyways will be exceptions where you deal with a throughly useless officer - these should be dealt with by complaints, they should be raised by the media, they should be tackled to prevent the same thing ever happening again, but they should not be taken as an example of what will usually happen.
*make up a subject - domestics, harassment, theft etc - and Google for police incompetence on that matter and I guarantee you hits. There is no anti cycling conspiracy.