When looking to the morality of any military conflict, we need to go back to basics, and to the principles of just war that have served us well since the time of St. Augustine. One of the key principles is proportionality. It is difficult to argue that, even if the kidnapping of two soldiers by Hezbollah was an act of war, that the response was proportionate, and therefore just. The Israeli response is designed to basically cripple the Israeli economy and weaken the fragile Christian-Sunni-Druze alliance that came together after the murder of Hariri by the Syrians.
Rather than just war principles, it seems that Israeli actions are instead guided by the lex talionis (law of retaliation)-- that Old Testament concept of an "eye for an eye". But such retribution, repudiated by Jesus, is explicitly ruled out by Catholic teaching.