In a broad sense, I don't object to the logic of "If we outlaw guns, only outlaws will have guns." The theater was a gun-free zone, which in the end only meant that none of the victims had guns.
HOWEVER, this theater being a gun-free zone had nothing to do with the government. The theater owners chose to enact a rule banning guns on their privately-owned property. Permit laws and whatnot may or may not affect public school shootings, but it could not have had an effect on this shooting, or any other shooting on private property, unless we were to enact laws making it illegal to not allow people to bring guns onto your private property -- which is not an avenue I think most sane Americans want to go down.
PERHAPS it's possible, though, that if we did ease up on gun laws and people got used to concealed weapons being legally carried at schools and other government buildings, private property owners (malls, churches, theaters) might feel more comfortable and ease up on their privately-enacted weapons policies in time, though this could take a generation or more.
BUT, all things being equal, if someone gets shot in my store, I'm less likely to be legally liable for it if I had a rule banning guns outright posted clearly at the door. Now, it's possible that if a good guy had had a gun in that situation, he might have shot the bad guy before the bad guy shot the innocent guy -- but even if that happened, that could potentially open as much or more legal trouble. If the good guy shot the bad guy too early, there's still a murder/manslaughter to clean up, and the victim(s)' family(s) can now try to make the argument that I fostered a dangerous environment by encouraging everyone to bring their guns to my CD store.
Target isn't going to be okay with people bringing guns into their stores. Whether or not it's safer in an individual store, it's much safer legally for the corporation to not be encouraging everyone nationwide to bring in all manner of weapons, and rather than get into drawing lines of saying exactly which types of knives and guns and crossbows are okay to bring into which stores, it's much easier to just issue a blanket weapon ban. Same with other chain stores. Now who wants to be the one store in the strip mall that doesn't ban weapons? If your customers do bring their guns to your store, now they can't finish the rest of their shopping.