There is a difference in a bookstore choosing not to offer select children's books because their content violates the owners sensibilities, and a mall preventing a bookstore to sell a children's book because the mall owner finds the book offensive.
Both are quite normal. What if the bookstore owner decided to only sell porn? The mall van decide to force the bookstore to stop that. That's just how it works. The bookstore is a client of the mall. So the mall decides.
