Greg Scoblete rejects the idea that Hagel would be more effective remaining as a critic of U.S. policies outside the administration:

This doesn’t sound very persuasive. Ultimately, if people sympathetic to Hagel’s views on various matters want their arguments to prevail, they’re going to need to wield positions of authority. That will naturally entail some compromises and deviations from time to time, but that’s inevitable. An ideological purity that never translates into policy outcomes isn’t worth much.

What makes Terry Michael’s argument even less persuasive than Scoblete allows is that Hagel would have virtually no influence as an outside critic demanding that Obama “bring the troops home now.” There is no guarantee that a Secretary Hagel would move the administration in the right direction on many things, but he will likely be a brake on military spending and future military action instead of a goad to both. The chances are good that he would be an advocate for withdrawing U.S. forces from Afghanistan as quickly and completely as possible, and he stands a much better chance of making that happen if he is inside the administration than if he remains outside it. If one wants to hasten the withdrawal of U.S. forces from Afghanistan, there are few things more useful to realizing that goal than to have a Secretary of Defense who argued that there should never have been an escalation there in the first place.

Regarding Scoblete’s larger point about maintaining purity vs. influencing policy, there is something else to add. Terry Michael urges Hagel to refuse to serve in Obama’s Cabinet in order to “make a statement,” but no one will perceive a Hagel withdrawal as a protest statement against “Obama’s war machine.” Even assuming that Hagel were inclined to make such a protest, everyone would see Hagel’s withdrawal as proof that the hard-liners and militarists (most of them in his own party) had successfully blocked him. No one would see it as a rejection of the “war machine,” but instead everyone would take it as confirmation that no one can offer even minimal dissents against hard-line policies without being barred from serving in important positions.

Activists and pundits often demand that a particular politician or government do something to “send a message” regardless of the efficacy of the action or how the message will be understood. It is frequently the case that the message that activists and pundits intend to send is never received. Because they fail to imagine how others will perceive it, they often demand actions that result in a worse outcome than if those actions had never been taken.