So, instead of cracking down drug dealers and gangs they decide to arrest a minor for making a list of how hot/ugly the girls are at his school? Glad to see the police force there is hard at work.
I would lean toward 'officer applying vaguely worded rules to make the law behave as he feels it ought to', but yours is certainly easier to get behind. Fuck the man!
The long-term impacts of individual actions on the power of the police-force as a whole are both non-obvious and very slow. In particular, I really doubt that the social pressure to empower the institution, transmitted down the chain of command, has more impact on police officers than the violence and abuse they witness first- or second-hand.
I'm sure that this is the explanation for much of the bad that we see, and as a result, those -- especially in politics -- who base their actions on demagoguery, attacking the individual parts of the system, are really doing nothing to help.
That would be a pretty crappy society in which to live. It's much better to devote some effort to the less serious crimes too. The more serious ones should be the priority.