While military action may be undesirable it is preferrable to alternative of nuclear armed Iran
At the end of the day, diplomacy may not be enough. The best explanation about why force has to remain an option comes from the IAEA director general Mohamed ElBaradei, who, on January 23, 2006, said "Diplomacy has to be backed up by pressure and, in extreme case, by force. We have rules. We have to do everything possible to uphold the rules through conviction. If not, then you impose them. Of course, this has to be the last resort, but sometimes you have to do it."To be sure, preemptive military force would be a highly undesirable option--but it would be less undesirable than the alternative, which could be both nuclear weapons in the hands of ideological hard-liners bent on confrontation and a nuclear arms race across the Middle East.
Iranian nuclear targets would not be buildings as such but rather processes, and, given the aiming information now available, they could indeed be interrupted in lasting ways by a single night of bombing. An air attack could succeed while inflicting relatively little physical damage and no offsite casualties, barring gross mechanical errors that occur only rarely in these days of routine precision.