I have worked in the Public Safety/ Private Security field for the past 25 years and have approached several people, especially at the apartment complexes that I patrol, the same way as Streetcar's hypothetical library employee and very rarely have I gotten a rude or defensive response. On the rare occasion that I did receive attitude from the person I explained that I was trying to keep everyone on the property safe including the person I was contacting.

I have found it's all in the approach. I try to treat people the way I would want to be treated if the roles were reversed.

LEOs have a very dangerous job and unfortunately it's very easy for them to fall into the attitude of "everyone's a suspect until proven otherwise".