it sounds like it was planned in advance...
The mall had had an earlier problem with "peace protestors".
Its private property. If they wanted, they could require every male to wear a collar and tie. Or every woman to wear a skirt.
"Peace protesters" don't need to shop there. If there are enough people in the "peace protester" crowd then the mall will go out of business as the stores will move out.
Nobody is stopping them from protesting in the town square (Unless the town has an ordinance that such a protest requires a permit...)
Scott