They're operating on your behalf when they're talking to other people.

When they're talking to you, they're your enemy.

I just don't think this 'enemy' rhetoric is all that accurate. Dealing with the police is like handling volatile high explosives; sometimes you have to do it, but they definitely have their purpose, but you'd be a fool to handle the interaction carelessly. Reducing that to merely 'enemy' conflates them with harmful things that serve no purpose at all. Like stupidity.

Seems a lot like a typical prisoners dilemma. Everyone treating each other hostile would give a worse overall outcome, but individually it seems like the best strategy.