A house, a mall, a office building, a road (unless public) are all private property therefore the private property rights apply. Your contempt for authority is trumping your respect for property rights here. As a private property owner or their agent (security guard) they have a right to ask a person to leave for whatever reason they want and set rules. They did not allow pictures being taken on property (for whatever reason) the security guard told them of the rule and told them to stop. They continued and so she told them to leave. They refused. Their refusal or failure to move off property is ILLEGAL and the security guard had the RIGHT to use a reasonable amount of force to remove them from property.
A property owner can not use force to stop you from taking pictures since it is not a law but they CAN tell you to leave their property. They can force you to leave if you refuse and refusing to leave is a crime.
I'm not saying the Guard handled this correctly but she did act within her rights.