If the US could make sure that the ENTIRE program would be destroyed by that and could do so without boosting the regime and embarassing the pro-western opposition in the eyes of their own people such an attack would at least deserve consideration. Possible implications like the Hisbollah opening a new front against Israel or Iran letting Iraq and Afghanistan blow up via their shiite buddies should also play a role. But since Iran is under any estimation still far from having a nuclear arsenal ready to be launched ( and it is increasingly unlikely the current regime will last long enough to see that day in office) we should not help them to gain credibility and it makes far more sense to focus on real threats like to keep Pakistans nukes out of the hands of the Taliban or to bring the Israel/ Palestine conflict closer to a reasonable solution. Because all sucessful efforts to calm the political temperature in the region will ultimately also have effects on Iran.