There are several reasons, write Michael Doran and Mike Rogers, among them:
Netanyahu’s speech is the act of a true and courageous friend. All of America’s traditional allies in the Middle East are deeply distrustful of Obama’s outreach to Iran. Allies in Europe and Asia are similarly fearful regarding what they consider to be flagging American resolve in the face of threats from Russia and China. Few allied leaders, however, will express their concerns to the president plainly—even in private—for fear of retribution. When they see the White House treating Netanyahu to a level of hostility usually reserved for adversaries, their trepidation only increases. . . .
[Furthermore, Netanyahu’s] views are reasonable, if not judicious. His opinions about the proposed Iran deal are not idiosyncratic; they are not exclusively Israeli; nor are they extreme. American observers with substantial reputations and with no ax to grind have themselves begun to express similar doubts about the proposed deal. Citing Henry Kissinger and others, the Washington Post editorial board recently wrote that “a process that began with the goal of eliminating Iran’s potential to produce nuclear weapons has evolved into a plan to tolerate and temporarily restrict that capability.”
If the president follows through with such a plan without first subjecting its terms to a rigorous debate in Congress, he will be concluding an agreement that is entirely personal in nature. The legitimacy of such a deal would be hotly contested, rendering it inherently unstable, if not dangerous. By helping to force a more thorough examination of the matter, Netanyahu is therefore performing a service to us all. When a president turns a deaf ear to a good friend bearing an inconvenient message, he works against his own interests, whether he realizes it or not.
Read more on Politico: http://www.politico.com/magazine/story/2015/03/benjamin-netanyahu-address-to-congress-115640.html