I'd love to see one of these snarly power-hungry dipshits try to stop me. Take my camera and I sue and/or file police report. Try to touch me and I sue for assault and battery.
Security is pretty much limited to escorting you out of the premises, they are not legally permitted to hold you (Unless they are actaully legally credentialed officers of the law, and you have to actually be violating a law, not a mall rule) and they certianly cannot start pilfering your private possessions.
Who the fuck to these people think they are? Try to stop me. The only law I break will be if I do not leave when I am told to leave. You can't stop me from taking pictures and you can't touch me or my possessions.