It always embarrassed Samuel Vimes when civilians tried to speak to him in what they thought was "policeman." If it came to that, he hated thinking of them as civilians. What was a policeman, if not a civilian with a uniform and a badge? But they tended to use the term these days as a way of describing people who were not policemen. It was a dangerous habit: once policemen stopped being civilians the only other thing they could be was soldiers.
Exactly. Which is why so many range from annoyed to seriously worried when cops do that. Borrowing a quote from another character in another time,
There's a reason we separate military and the police: one fights the
enemy of the state, the other serves and protects the people. When the
military becomes both, then the enemies of the state tend to become the