Suppose a little 120 pound man is living in peace and minding his own business. A huge 600 pound monster threatens him with death, and prepares to murder him. The little man kills the 600 pound monster in self defense. Can the little man be blamed? Of course not.
Israel is constantly threatened with destruction by a much larger nation, whose actions constantly prove it murderous and sadistic intent. Why should Israel wait around? Israel would be fully justified in using EMP on Iran right now, and sending it back to the Stone Age.