I'm not sure how apropos that is, however. It is generally accepted that armed policemen and security guards are deterrents to the badguys. In fact, very often that's why companies and organizations ensure their presence.

That to which I'm referring is an armed civilian who intervened in a mass shooting situation. Now, that person would rightfully be considered a hero, and deserving of the NRA billboard, which would be put up as a 'community service'. And the NRA uses that scenario as a good reason for continued liberal gun laws.

However, despite those liberal gun ownership laws that situation doesn't seem to have occurred. Despite an average of 20 mass shooting events each and every year, year in and year out. You're right, though, the presence of policemen and security guards does seem to have an inhibitory effect upon the more egregious forms of anti-social behaviors.