He is off duty and paid by the business, there is nothing illegal about but if you choose to get all butt-hurt about it then so be it.
Its legal for now, and until Georgia changes that law its a great way to make easy money. We already don't get paid a lot in this job and the side jobs help.
I choose to hold people to the law. Cops included. That means that using public property to make private money, called misappropriation of public funds, needs to apply to moonlighting cops as well. If cops want to work security using their training I think that's great. As long as they buy their own uniforms weapons, ammo and equipment and do not present themselves as police. A security guard who presented himself as a cop would be guilty of impersonating a police officer. A cop in private employ should be guilty of the same if he is representing himself as a cop.