Duncan's experience is absolutely in accord with mine: People who carry concealed - and let you know it - are just looking for an excuse to use it. If they've been at it for any length of time, they've got at least one story about how they brandished it and made some punk run away in fear, a story they tell with great relish right after they show you their piece. The psychology of it is a total mystery.
I have experience with firearms and, given my temperment, I'm terrified by the idea of having a gun on me while driving, or at a bar after having a few drinks. So I have excellent reasons not to carry and no really good cause in the other direction.
People who say they have to carry concealed because of where they work or live have a very high standard of proof to meet, from my perspective. "I live in the city" certainly doesn't cut it. "I live in a really bad neighborhood" starts to get them there, but I would first also need to hear about how good they are at spotting trouble before it gets to them. If they don't have any stories about doing that, or worse, say they shouldn't have to avoid some situations, then they fail to have the proper mindset. Also, I have lived in the city for decades, and I know my definition of "really bad" is much different as a result.
Next, I don't care if they have the "Stand Your Ground" law in their state, if they don't readily acknowledge that their first duty is to retreat in any dangerous situation, then they fail. You are not a superhero. This is not a movie. If someone pulls out a gun and you can get away (with the people you need to protect), then get away. All else equal, if you don't pull a gun, there is a much lower chance of a gunfight. And fewer gunfights mean fewer dead and wounded people.
There is much more, but the above will eliminate most candidates.