Egypt had closed the Straits of Tiran, an act of war, and had made several other very provocative moves. One dosen't need to absorb the first actual blow to be at war. Sometimes, in special situations like 7/12/41, it is useful, but Israel chose not to that time. Egypt did indeed start the 6 Day War, by any fair analysis.
UN: Gaza could be 'uninhabitable' by 2020 if trends continue (AP)
from the article: Four Gaza factions halt rocket fire, in bow to Hamas