I don't particularly like that metaphor either.
There's a variation of it that is more realistic in my opinion.
There are sheep (= brainless followers, basically everyone who's being controlled, a group which includes the everyday worker, small time criminals, basically everyone who's all the way down in the food chain)
Dogs (= a group that is used to control the sheep, they think they're doing good and probably are as they keep everything together, but they don't realize they're being used by the pigs, ultimately the good guys in this metaphor, mostly people who have a job with the state and politicians)
And the pigs (= the ones on top of the food chain, the people who are actually in charge of everything, may include politicians but mainly big time business owners, weapon's manufacturers, oil concerns, people with lots of money and influence who belong to certain lobbies - note that there are no actual criminals in this group).
The sheep don't give a crap about anything because they don't have a brain of their own. So they let the dogs control them because that way their peaceful life is not disturbed. They like the dogs for that. The dogs think that there's nothing bad going on and keep doing their job never asking 'why?'. That way the pigs use the dogs who are both somewhat gullible and well-intentioned to control the sheep.
If you see it that way the ultimate goal is to either not belong to any of these groups or be a dog in pig's clothing.
Yes there is a certain amount of politics involved in law enforcement. At the end of the day, I truly believe it's as basic as good versus evil.
There are bad people out there who take advantage of society. Then there are people who keep society civilized and hunt the bad people. Even the pigs in your metaphor need the dogs. The pigs are part of the sheep in my metaphor.
To simply say that you aren't a part of any group is a false perception of reality. You can be the most educated, self thought out, original person in the world. That means squat when you are in a public place and a mass shooting starts. Next thing you know, you are praying for a sheepdog to show up.
It is similar to having a heart attack and praying for an ambulance or doctor to show up. (nothing high and mighty meant about needing law enforcement)