How is that childish? Do you know how much money they put into advertising these films, and just have another film with the same title getting free publicity by the mere fact of confusion, do you think a studio or a director would want that for their property? Talk about fanboy critism.
Shymalan is already filming his movie and it'll be called the Last Airbender. I don't blame him either for trying to get the title because it's the name of the cartoon. Now if it was the other way around and Cameron was the one trying to get the title would it be childish for M Night to try to keep him from using the title? Besides, the directors don't have to lift a finger. The issue arises and the lawyers get to work, if Cameron would have lost there would be a new title for his movie, it happens.