Why did Obama choose to stand down?

Paul Mirengoff at Powerline tries to assess the administrations's actions and inactions in Benghazi. He concludes: "(1) the administration erred grievously by leaving open our mission in Benghazi while turning down requests for more security, (2) the administration made the wrong decision on the day of the attack by not bringing our military to bear, a decision consistent with Obama’s instincts, and (3) the administration has not been forthcoming or honest in its discussion of Benghazi after the fact. These facts, without more, present a serious indictment of Obama.