I really don't think you're understanding the situation and are displaying a lot of misplaced anger.But if the cop is off duty he is NOTHING but a security guard. When employed by someone other than his department a cop is nobody special.
Define "color of law".
First of all, as Dennis stated, cops don't become "not cops" just because they're not "on duty". I have full authority to make an arrest "off duty" so long as I follow my department's SOP's (ie. have badge and gun).
Second, the cop isn't a "not cop" because he's working he's doing extra duty work at the movie theater. I'm sure every contract is different but its a contract between the business and the department. We as individuals don't just go up to a business and say, "Hey, I'm a cop and have a badge and a gun that I'll bring with me if you hire me." Not quite how that works . . . so, please do explain the misappropriation of government funds (or however you put it) because I'm not seeing it. The business didn't hire a security guard, they hired a police officer from the police department.
Here's what I'm seeing. You're angry because the business gets to make a stupid rule about not allowing guns. I agree, it's pretty dumb but it's their right and we certainly don't want to go around violating people's rights now do we. You can't take your anger out on the business because as I just stated, it's their right. So, who next? Oh yeah, the guy that gets to confront you about the stupid rule. Well guess what, it absolutely makes no difference if it's the kid selling popcorn, an unarmed security guard, or a police officer. They all have every and equal right to ask questions and if the business and its management so chooses, to ask you to leave the property.
You're upset because with it being a police officer because if you pitch a temper tantrum you will be arrested (and you will be when it rises to the point of Disorderly Conduct which is a violation of State Law). If it was just a popcorn seller or a guy with a badge but no gun you could pitch your fit and then leave before the cops got there.
There are no public funds being spent so your argument of "your tax-payer money" is ridiculous. If the business wanted a security guard they would have hired a security guard. No, they wanted a certified law enforcement officer, so they contacted the police department, found out how much it would cost to have a uniformed officer with a patrol car posted there and then they paid XX amount.
It is absolutely no different then business staff seeing you with a gun and then calling 911 to ask that you be removed. Only in this case the business paid the police department to have a cop stay there and not be distracted by other 911 calls.