Argument: Missile defenses can counter only minimal, unsophisticated threats
"Slovak prime minister slams U.S. for missile defense adventure". Reuters. 27 Jan. 2008 - When discussing the proposed missile defense system for Eastern Europe, it's best to put the word "defend" in quotes. This is because the missile defense hardware United States is deploying in Alaska and California, and is proposing to deploy in Eastern Europe, has no demonstrated capability to defend Europe, let alone the United States, from an attack by Iran (or North Korea for that matter) under realistic operational conditions.
For this reason, the U.S. Missile Defense Agency has "dumbed down" the supposed threat from Iran (and North Korea) by definition to be just one or two missiles with no decoys or countermeasures. And yet still the MDA has not been able to demonstrate the effective capability to stop even that idealized threat under realistic operational conditions. Seven of the 13 flight intercept tests conducted with the Ground-based Midcourse Missile Defense system have resulted in successful intercepts, but six have failed for one reason or another.