If a "good guy with a gun" is running towards a shooting, that person is not within the bounds of the law (self defense), and might compound the situation. Concealed or open carry is to defend yourself and others if you feel your life is being threatened. If you seek out a shooter in a public setting, you're not defending yourself. If it's on your property and presents a threat to your loved ones, then the use is justified. The largest content of concealed carry classes is the legal aspects of using your gun, not how well you can shoot.

I live in the wild west of Kingman, AZ. I'll admit to occasionally carrying my single stack 40 cal. Like Dustin, I try to avoid places where I feel like I should carry. I don't feel threatened at home, I live in a nice area with large lots and neighbors who are at home most of the time, but there are places in town where I'd never live. I went to Walmart to look at slow cookers two evenings ago and I saw more than a dozen people open carrying (perfectly legal in AZ) in the store. There were likely just as many with concealed carry. People feel the need. I have to local news on my FB feed and the reported shootings almost always involve drugs, mostly meth. There are places in the US where a person with a pistol on their hip would cause a panic, but this country isn't a homogeneous population and there are places where it wouldn't get a second glance.