Remember, guns are banned in the Post Office not because of actions taken by people at the customer counter but because of Postal Service employees going nuts.
It think saying that guns are banned at the post office due to the actions of their employees give the tyrants too much credit. Guns are banned at all federal buildings, including national park visitor centers. Your masters ban guns anywhere they can conceive of an excuse to ban guns, because they believe that a disarmed populous is easier to control.
I’ll bet that a large percentage of the violence at POs involved love triangles.
Totalitarian, citizen disarmament extremist always say “here is a problem, here is what I want to do”. They expect you to think that since they said those two things in the same sentence that they are related to each other, but they don’t ever actually claim that. If you push them, they won’t try to support the ridiculous notion that putting a sign up at the post office, a school a mall, or wherever could possibly prevent a crime there. It would be stupid for them to say that, and they don’t ever say that. They just say “something needs to be done” and they are very clear that “something” doesn’t need to have any logical chance of solving the problem.