Never met the type myself, but... if they are bothering you as you taxi in with their big shiny 'f*ck off' maglite then give them a few bursts with your landing and taxi light. That'll generally get them to avert their gaze!
Agree with you about the ARN bit though. Ask them what part of Aviation Legislation they are upholding by requiring that information and on whose behalf they are working for, their name, rank, 'badge' number and so on. I bet their questions slow to just a trickle after that.
Probably just Shopping Mall security guards who now get to carry a gun on a bit of an ego trip. Kind of like when new CPL's get to put on all their gold stuff to go down to the corner store to buy milk and bread at 0700 on a Sunday morning.
Twin