the idea of the US government bombing, say, Milwaukee to kill a hundred partisans is a much better comparison. Alderaan wasn't at war with the Empire, it was a MEMBER of the Empire.
It seemed from Tarkin's statement that "rebel operations on Alderaan" had little to do with the reasons for targeting it. " Not remote, so makes a better demonstration than targeting an actual Rebel Base" is an almost word-for-word paraphrase of the reason he gives.
Edited by Ironlord