Five years ago I had a Total Hip Replacement and part of my therapy was to walk with a walker (53 yo). The mall was the easiest and coolest (OKC, OK in the summer
).
The first time out my wife takes my DSLR to "document" the recovery. She was chased down by a Mall Cop and threatened because of the security breach. Didn't she know that after 9/11 there was such a possible terror problem and photos were not allowed in the mall. He could confiscate the camera if he wanted! 
It was absurd!
I'm pretty sure they can't confiscate your camera, but you can call the cops on them for grand theft and assault if they try. Just offer to bag your camera and stop shooting, or leave if they ask you to, but if they try to take it forcibly... 911.
Also, some of these cowards like to pick on an easy target. They probably saw you with the walker... Not all guards are bad, there is just an element of scum that you need to stand up to every now and then.
I had a meltdown on a guard once, I can't remember where, but I was out of NYC at the time. Whatever it was, it was just ridiculous. I knew it, he knew it, it was dumb. Like telling me I can't eat in the parking lot after ordering from the drive-thru:
Me: "So offended that you even dare mention 9/11 as a reason for your bullcrap. I am from NYC and was born and raised in lower Manhattan, how dare you use that tragedy as an example of why I can't (can't even remember the stupid thing in question). Just admit it is this some stupid policy you have?"
Guard: "yes. I'm sorry."
Sometimes it's not even about 9/11, just them being "authoritative" which is what they teach in security school. However that should be practiced with discretion as sometimes politeness works better, other times lying (ambiguity) is better but in a careful manner, and other times flat out assertiveness is called for. Here are some examples:
Wife with DSLR: "Excuse me ma'am, mall policy states... and I don't want to ask you to leave, so I would appreciate it if you put the camera away."
Suspicious package, etc: "Ladies and gentlemen, we have a maintenance issue in this area and need you to clear away from it temporarily. Please keep moving in that direction following the officer's instructions.
Confirmed bomb: "RUN FOR YOUR LIVES WITCHES THERE'S A BOMB IN THIS MOTHER."