There are still rockets flying out of Gaza into Israel.
> 2. Its only purpose is to defend against the agression
The people sending those rockets are in Gaza, so to stop them, Israel has to go there.
> 3. The defense has to be proportionate
That one is regularly the most difficult point of contention in individual self-defense. Hamas essentially goes by this playbook: https://imgur.com/XX6HVrn
So, moving it back to individual self-defense (or coming to somebody's aid, which is covered by approximately the same rules): what should be done about the guy holding a loaded gun at his hostage's head while covering himself in babys?