The police report said they were stopping other shoppers
If true, that would be a violation and was probably the reason they were told to leave. As much as these guys want to claim their rights, the other shoppers also have rights not to be harassed. It would be no different than the mall getting rid of a cad who was harassing women. Simply because someone believes in a cause, it doesn't mean his rights outweigh everyone else's.
If it was simply a matter about the wording on the shirts, then the case would be very weak if they weren't stopping other visitors. I don't know, but I suspect there is more to the story as the police report alledges.
In the end, it appears the mall is dropping the charges.