Back when I was working on mobile CAT Scanners, I often had to work at MLK hospital, in Watts, California. This was back before hospitals had their own scanners, so the mobile parked at a loading dock near a rear entrance to the ER. One night I was talking with a cop at the local Winchell's, who told me I was crazy to work at MLK without a gun.Thank you. My wife and I live about 20 minutes from the nearest law-enforcement response in the event of a 911 call, unless some county deputy or state trooper just happens to be driving by when the call comes in. I'm not going to negotiate with some creep on the other side of my front door, or someone who climbs in through a smashed window. That would be a dead person.
I never open-carry handguns, though I can. It's just not in my makeup. My youngest sister has a concealed-carry permit. She has worked at a home/school for troubled youth and moonlights as a bartender. She never knows if she is going to be targeted when she sets out on her pre-dawn walks. I don't think that she is capable of pulling that trigger when there is a human at the other end, but at least she has a deterrent.
As has been pointed out, when you REALLY need a cop, you rarely have the time to wait for one or even call for help. You are most likely completely on your own. It is up to you to live or die. The first time someone points a gun at you, that becomes abundantly clear in an instant.
As for this law, it makes sense to the extent that potentially dangerous people might be caught or held before they have a chance to do harm. And it does eliminate the need to show intent if a suspicious character is found to be carrying a weapon at a political rally. I would be worried about when and where it applies. I would think it would have be limited to government buildings and formal political events. In those situations, rather than having an armed audience, it makes a lot more sense to have a few designated individuals carrying concealed weapons.
Having the ability to wear an AK-47 at a political rally, as happened a while back, is just nuts. And doing this won't act as a deterrent to mass murder. One reason we know little about mass murderers is that they usually commit suicide during the crime.