"Why discuss his religion or his training as a psychiatrist in the context of his killing spree?"

An indication that religion may be implicated in his motivation:

"Soldiers who witnessed the rampage reported that the gunman shouted "Allahu Akbar!" - an Arabic phrase for "God is great!" - before opening fire, said Lt. Gen. Robert Cone, the base commander. He said officials had not yet confirmed that Hasan made the comment before the shooting spree."