Im not going to came here with 200 pages of data, pools or evidences, im just going to give my own opinion its a conditioned one tough.
Like all the ppl in the world there are bad and good cops, and a great spectre between them. The concept of security forces appeared for the fisrt time in past old days when rulers, wanted privileges and used the security of their ppl to make this "cops" (wich made some security job but well, their first works where the protection of the status, rulers with lots of priviledges and worker-slaves) this happened in all cultures arround the world for the last thousands of years.
Our police corps, i mean on 1st world states are the lesser evil, wich at sometimes is the greatest good (i remark sometimes). The problem of this corps is that they are conected to their superiors, chiefs-ministers-politicians etc. We live in a quiet corrupted world (this isnt something new for any1 is it?), those police workers (the ones that made the real job) have to do what they are told by their supperiors, which sometimes isnt to look for the citizens protection at all, or they justify that citizens need to be protected from themselves (a dangerous path to take).
In my country there was a terrorist attack on some trains more than a year ago. 200 killed and thousands of injured. They made the investigation and found out that the explosives sold to the terrorist where explosives that one of our (police-military) security forces gave to an informant, who sold them to the terrorist, and no1 did anything. And that is only the begining of the story, keeps going with chiefs that sold weapons to ppl, polices that shot 20 times an informant who was on the plot etc.
The investigation was closed fast and without searching the truth (not because they were the terrorist and guys who put the bombs, but because they cant afford to make public how bad the things work in our country, and show that they dont have much control of things going on: the greatets fear of a state is to reveal that it doesnt work, they are being paid for nothing, they are weak).
This is just an example, the worst, but this kind of things turn any good job they made in to shit. I could speak a lot more but sadly english is my 3rd lenguage and i wouldnt be able to explain myself to well.
Bye.