Nice to have some confirmation as to how much good

"No weapons allowed" signs do. The whole article is on LE response to an active killer, here's the part I'm specifically referring to:
The other statistic that emerged from a study of active killers is that they almost exclusively seek out "gun free" zones for their attacks. In most states, concealed handguns are prohibited at schools and on college campuses even for those with permits. Many malls and workplaces also place signs at their entrances prohibiting firearms on the premises.

Now some tacticians believe the signs themselves may be an invitation to the active killers.

The psychological profile of a mass murderer indicates he is looking to inflict the most casualties as quickly as possible. Also, the data show most active killers have no intention of surviving the event. They may select schools and shopping malls because of the large number of defenseless victims and the virtual guarantee no on the scene one is armed.

As soon as they're confronted by any armed resistance, the shooters typically turn the gun on themselves.

And in the update, they list the information to back up the 'invitation' point, including
Based on data from the SEALE study, an analysis by TDI, and our own painstaking research, we are able to say definitively that most "active killer" shootings have occurred in so-called "gun free" zones. The experts who say they may be "invitations" are also John Benner and Ron Borsch who have six decades of law enforcement experience and training between them.

And they end with evidence that there actually are reporters out there who believe in reporting facts, whether anyone likes them or not:
As journalists, we are not interested in entering into the heated debate over gun control. We are, however, interested in reporting the facts. In this story, the facts point to the active shooters ignoring gun prohibitions and perhaps selecting those locations because they are "soft targets" where no resistance would be found.