The mall property is owned by someone - be it a corporation, a private person, or a group of private people.
The manager’s job is make sure the business runs smoothly, efficiently, and profitably. And disturbance free.
If the manager is acting in concert with the wishes of the owner(s), and they have a policy in place to remove what they consider a disturbance, then he is within his rights.
And as for my property, if someone decides to hold a prayer meeting on my front porch, I can guarantee you my local law enforcement will remove them at my request.
Nothing “cute” about it. That’s all there is to it.
I think that you are confused in your concept of “private property” VS privately owned public property. At your residence, your home is pretty much your castle. But things that you can control there, may not apply at say your laundromat or Woolworth lunch counter (try hanging up a sign saying “whites only” or “ Colored not allowed”). I think that you will not get much cooperation from law enforcement in enforcing your signs.