While the deep roots may help us understand the mutual fear and loathing between on the one hand Israel and the Lebanon and on the other hand Israel and Gaza, it still does not to my mind justify the disparity between the specific attacks by relatively independent movements against Israeli soldiers on the one hand and the responses by the Israeli state against the civilians and infrastructure of Gaza and the Lebanon.   

The particular attacks, resulting in the kidnap of soldiers, were not themselves "terrorist attacks". They were not themselves attacks on civilians.   The Israeli response has been very substantially against civilian persons, and almost wholly against civilian infrastructure. These particular actions and responses seem to my mind different in kind from the widespread tit-for-tat-ism of the region.

Imagine that the IRA had shot a British soldier. Would that have justified England blasting the Irish republic back into the stone age?

Imagine that the USA had been funding the IRA. Would that have justified England nuking the pentagon?