If an asteroid mission were a priority, NASA could accomplish it much sooner (and more cheaply) using systems such as the Space-X Dragon capsule and Falcon launch vehicle, Atlas and Delta launch vehicles, and Bigelow inflatible habitat modules, which are already in production or in advanced states of development. To delay a human asteroid mission for the development of Orion and SLS is akin delaying the US entry into World War II so Howard Hughes could finish developing the Spruce Goose, instead of using the DC-3. It makes no technical, economic, or programmatic sense. General Bolden must know this, if he is getting competent technical advice.
Of course, space cynics will say that Dragon and Falcon are still in development. Commercial programs can (and often do) fail, as former NASA Administrator Mike Griffin is fond of noting. Griffin errs, however, when he implies the contrapositive position — that non-commercial programs never fail — which is provably false. There is no reason to believe that Dragon and Falcon (which are farther along in development than Orion and SLS) are more likely to fail than Orion and SLS.