7 years as an aircraft mechanic in the United States Air Force,
Here in Missouri there are no state mandates for security guards. That can change on the city and county levels. Some training may be required by the hiring company and this training may consist of classes in the role of private security, legal aspects, state laws, incident response, CPR and first aid.
Security guard is visible in a store = a person may be less likely to shoplift or attempt to swipe someone's wallet.
Security guard is present in a bank = a person may think twice before attempting to rob it.
Theories, right? Suppositions. The leap-before-they-look types and folks who don't tap the ON switch attached to their brains when they start a day totally blow these premises out of the water. THOSE people are the ones security guards get to tangle with.
Anyone who's had to work with the general public knows there will always be people who test your patience and good nature. Joe's way of dealing with them is to do what he's got to do on the job and then laugh about it later.
An excellent solution to not letting hard-to-deal-with people get to you, don't you think?