1) The Iranians do not yet have a nuclear weapon.
2) Even once they get such a weapon, they still have not developed a delivery capability that the missile defense system is targeted at stopping.
3) We have no evidence that the missile defense system under consideration would actually work.
Taylor--no pacifist--admits that if there were anything to be gained from a missile defense system, he'd think differently:
Look, if what the Obama administration was doing was giving up a reliable (if not foolproof) defense against an actual existing threat, then I, too, would find the move problematic. However, again, this is not the case. We are talking here about an unproven, theoretical defense against theoretical, not-yet-existent threats.
As others--such as the Atlantic's own Marc Ambinder--have pointed out, this suggests that much of the conservative chest-thumping over the missiles has less to do with geopolitical concerns than with a simple "gut response":
"Missiles in allied countries pointing at Russia GOOD...taking them away....WEAK.....Russia...BAD."