There's a double edged sword here.
How does this change random drive bys, muggings, and the like? How does that prevent a guy with a gun from going onto campuses and opening fire still? People will still die from gun violence. Besides, you kill the gunman. He still got someone and he died, too. I haven't seen a gunman that opens fire on a school ground live in 10 years now. He still got what he wanted.
Say you have a gun on a plane and a terrorist tries to take control. Safety in numbers. They can carry then, too. More terrorists with a planned attack to take control. Then they can have people watching for those who want to step up. It wouldn't be a knife to slit a woman's throat. It would be a 9mm at her head. I still can't see it working out to be much safer.
I'm not looking to start a war of words here, either. Especially with you, Spy guy. But, I think, in the wake of some of the gun violence, this counterpoint should be equally voiced.
I still sit on the fence with this, but I find that I lean toward no conceal and carry laws