If my memory serves me right, Lacus responded after Durandal fired that doomsday weapon to other countries first
Now comes the irony part, had Durandal only proceeded that Destiny plan to Zaft's territory, then it bears no meaning at all..the whole point of the plan is to end the war, so you have to include everyone, and when you try to force other countries to comply, fight sure will happen...and it gives Lacus's excuse to fight back as soon as Durandal fired that doomesday weapon, it should have fired at Orb first
That being said, it is annoying that Kira not fight with blue comso at least once...that was the bigger evil before Durandal took over