Interesting that three out of your four encounters with cops were positive experiences (I won't count what they did today as a positive or a negative experience, because I don't know if your housemate did something serious that easily justifies busting in in the middle of the night), yet you are not particularly fond of them merely because of their media image!

Just as with any subsection of society - computer programmers, scientists, potato chip manufacturers, you name it - there are going to be good people and bad people. But cops have two problems:
1. They are in a position, much like surgeons and politicians, where their decisions have far-reaching and serious effects. If a technical writer like me screws up, the worst that can happen is an instruction manual has a spelling mistake (and in the vast majority of cases it won't affect understanding). But if a cop screws up (or does something on purpose), people die.
2. Cops are in a position of legal authority, which means they face a great deal of resentment - both from the standpoint of the individual who hates getting a traffic ticket and from the standpoint of the many segments of society that hold an appreciation for anarchism.

I hold a great appreciation for cops - when they do their jobs. In America that was always the case, and I knew I could depend on my local police to be courteous yet firm, tough but fair. Here in Israel, the cops are made up of anybody who wanted to enter permanent army service but couldn't cut it, so they have a well-deserved reputation for laziness and incompetence. But that's still a far cry from seeing them as actively antagonistic. Just like there will always be evil/sadistic computer programmers, there will always be evil/sadistic cops. But in a modern, free society it's unheard of for them to be a significant percentage, no matter what impression you might get from the media.