Eghad, you are right. I have had the misfortune to have the need to deal with about 30 cops over the last month or two, but the good fortune to find out that they're mostly decent people. As a matter of fact, I'd estimate I have met, briefly, maybe 50 cops in my lifetime. Only one appeared to be a prick, but I was a teenager and he and his partner, looking back, were playing a good cop/bad cop game with me to do me some good.
I happen to live in a neighborhood where a large fraction of the homes are owned by cops or other justice-related people. One neighbor is a juvenile corrections officer. He gets certain "courtesies" that I'm aware of. But apparently precious few.
Another neighbor was giving him trouble a few months back. The sheriff's deputies seemed to treat him the exact same way as I was being treated. I didn't see any preferential treatment, and I saw the police out at his house several times.
It should be obvious to anybody here by now that I'm a pretty anti-police-state kind of guy. But somebody has to manage the criminal element. Like any other field, you treat your professional peers with more respect, usually, than the general public.
I'm going to take the word of the guy at the desk next to me with whom I've worked for years about ion migration in semiconductor passivation over the word of the next guy who walks into the building's front door looking for an address. Every profession has that. Cops are, I'm sure, no exception.
Unfortunately, I think two things come into play here that aren't present in other fields. One, cops can affect your freedom. Semiconductor engineers really can't. Two, cops interact with a great variety of people. Some treat them in a businesslike manner, even if they're about to be ticketed. Others give them lip and lame excuses or worse, just for doing their jobs. I'd bet the former group gets the actual ticket less often than the latter.
So a little bit of this "professional courtesy" stuff is nothing more than behaving in a professional manner, i.e., with ordinary business courtesy. People in the general public who do this probably are treated favorably. Other cops probably know to behave this way, and are also treated favorably.
Sometimes, as we saw in another thread, even a cop who self-righteously insists on "professional courtesy" while acting like a child doesn't get any. That's probably because cops, on average, realize that favoring a jerk paints themselves with that same brush in the public's eye.
My point is that it's not as bad as it looks, but it's not as good as it could be, and that some here DO realize it's "cop" and not "cops".
As a concrete example:
Recently I had a big legal problem with somebody. During my dealings to corral his behavior, I noticed his car tag belonged on another car. I could not get the police to go to his place and ticket him for this. Now, I am SURE if a cop were having this same problem and this same information came to his attention, he would work out a way to camp out by this guy's driveway until he backed out and then ticket him.
You could look at that situation and conclude that cops get and give themselves preferential treatment and be unhappy about it.
However.
In a past life, I designed digital video systems. In order to help myself with this same legal problem, I needed some fancy video surveillance. I got it at a very minimal price. That's because I had the means to do it myself. If a co-worker asked me for help doing the same thing, I'd help, knowing he could handle the heavy lifting and just use my ideas. If a cop or anybody else asked, I'd say no. Why? because I would end up doing the whole job and I don't have time for it.
It's the same thing. Are there abuses? Of course, like anything else. But in any profession you are in you can get a thing done that's the subject of that profession easier than you can get a thing done that's not.
Wouldn't surprise me if there was a felony in there. 
