WASHINGTON - Army superiors were warned about the radicalization of Major Nidal Malik Hasan years before he allegedly massacred 13 soldiers at Fort Hood, Texas, but did not act in part because they valued the rare diversity of having a Muslim psychiatrist, military investigators wrote in previously undisclosed reports. An obvious “problem child’’ spouting extremist views, Hasan made numerous statements that were not protected by the First Amendment and were grounds for discharge by violating his military oath, investigators found. Examples of Hasan’s radical behavior have previously been disclosed in press accounts based on interviews with unnamed Army officials, including...