(Image: Blue Star Families)When he grows up, 6-year old Walker Greentree wants to be a SEAL—a member of the special forces of the United States Navy. While he was playing with a friend, his mother scolded him for being noisy and told him to be “quiet like a SEAL.” Walker’s friend insisted that ninjas are quieter than SEALs—a proposition that Walker heartily disputed.In order to resolve their argument, Walker wrote to Admiral William H. McRaven, the commanding officer o...