However, I also know that when I see my coworker running a server on the side, watching youtube videos, or whatever else might get him fired, I'm probably going to give him the heads up that what he's doing probably isn't the best thing if he wants to stay employed. When the manager finally catches him, I'm not going to stand up and say "but you don't understand our jobs" and try to actively cover for him so he doesn't get fired. If someone from another department starts talking about it, I'm not going to try to defend the behavior.
This is where I have a problem with the argument about how I can't judge all officers by the acts of a few. Ordinarily, I'd say that's so. However, when they do such a piss poor job of policing themselves and such a good job of backing your buddies even when they're caught on tape egregiously violating their code of ethics or someone's civil rights, then I am going to lump everyone in the same group.
Basically, there's a difference between "ratting out your work buddies" and "covering up for and backing your buddies even after they've been caught and the manager is threatening to fire them". The former is unfortunate, but expected. The latter is unacceptable and makes you complicit.