No, they're not private security guards per se, but if they're not being proactive in apprehending criminals, it does SOCIETY no good, nor the individuals therein.
That being said, if the SCOTUS believes that, then they should also have no problem with me enforcing Castle Doctrine in my home, period. At least in NH, even if a perp is still ON YOUR PROPERTY, not just in your house, you have the right to use deadly force.