Using Wal-Mart's shopping carts to place littera-trash? If I was the manager, I would not allow that--if they were going to do it at all, the rules would be that they not obstruct traffic, excessively hound passers-by to accept anything, and that they had to use their own equipment to store whatever littera-trash they used. And, if they abused the privilege, it would be retracted--along with making it equal opportunity for any religion to set up a booth next to the witlesses under the same rules.
Some things I find objectionable include blocking aisles of traffic, blocking people from freely getting into or out of the parking lot, going after everyone that tries to just enter the store, excessive shouting and yelling to draw attention to the group, use of store property (such as shopping carts) to store and display littera-trash, leaving littera-trash in places where it makes extra work for maintenance (you bring it in, you take it out), and steering customers away from seasonal displays. For sure, if I saw a group of witlesses chiding someone for buying sun-worship decorations or flags, that would amount to interfering with the business and result in retraction of the privilege. And, if enough customers complained about excessive blockages, pushiness, or that they are going to L.L.Beans to avoid those pests (and not just for better quality), the privilege would be retracted.
Now, how many Wal-Mart flyers are Wal-Mart managers allowed to distribute at Grand Boasting Sessions? Or at the Kingdumb Hells? I don't think so. Things like that are what the witlesses need to think about: Distribution of literature or solicitation on store property is a privilege, not a right. Whether it is the witlesses, the Twelve Visions (or any other) political party, or a school event, they need to abide by the same rules and realize that they are dealing with a business. Except charities that the store itself is sponsoring, the manager has the right to refuse any other solicitation for anything, with any or no reason--especially if there is a sign explicitly banning it.