Barely 24 hours into Operation Northern Arrows and the Christian militias became visible cordoning their areas off for Shia refugees. I wouldn't call that unity, more like ancient simmering blood feuds springing back to the surface. Lots of bad blood and unfinished business in places like Lebanon - and when the current top gorillla gets clapped around NSFW style the alpha males one or two stairs lower on the monkey rock take note and ready themselves to take benefit of that opportunity.
The different Lebanese sects have segregated their entire society just to not have to deal with each on a daily basis. I give it no more than 4 weeks max from the moment the first IDF tanks cruise into Southern Lebanon to the moment the bullets start flying between the warring factions in Lebanon.
Here comes a groundbreaker: Hezbollah and Iran are some of the most hated entities in Lebanon and the Middle East. Probably even more so than Israel. The Syrian Civil War did the Sunni Arab psyche dirty, just like 100 year of distrust, power play and intermittent conflict turned Lebanon into one of the most sectarian countries on the planet. Don't let the narrative pushers fool you, they are aiming for gullible yet well meaning ignoramii anyway.
Another groundbreaker, and one that seems to be a carefully revised, spun away or outright ignored: many of Lebanon's Christian parties have been cooperating with Israel for decades. Like you stated, the Phalangists committed that massacre in the Palestinians camps of Sabra and Shatila on Ariel Sharon's watch - the IDF established a perimeter around the Palestinian/PLO camps and in went the Phalangists to do the killing. Many such cases. Israel's main proxy during its occupation of Southern Lebanon (1982-2000) was the Southern Lebanese Army - a Christian dominated force whose families were coerced by Hezbollah to leave the area after the Israelis retreated.
Why anyone would think this time it's going to be different is beyond me but hey, propaganda is a hell of a drug.
A lot of the Christian resentment stems from a feeling of unjustice. Especially the Maronites consider Lebanon
their country - and say that many of the Muslims are not native. They have a point: the French founded Lebanon as a Levantine refuge for especially the Maronite Christians. A Christian last stand in the cradle of the religion - at a time when Lebanese Christians still constituted a majority population wise. Lebanon was a relatively rich and advanced country - Beirut the Paris of the East.
Fastforward 100 years and Lebanon has become a failed state and economic basketcase, de facto ruled by Islamic fundamentalists that are on a foreign payroll. Demographically the tide likewise turned. Many Lebanese Christians emigrated to places like Brazil, Argentina and the US, and in came waves of Palestinians (1980s, setting off the Civil War) and Syrians (2010s). Muslims had a higher birthrate than Christians on top of that.
The breaking point was the signing of the Taif Agreement in 1989 - the conclusion of the 15 year long civil war. It broke the Christian hold on Lebanon's political system - something that was later exacerbated by the further rise of a well organized and armed militia on Lebanese territory: Hezbollah.
The majority of the Lebanese Christian political establishment is opposed to Hezbollah. Kataeb and the Lebanese Forces (LF) are part of the March 14 coalition, which is in opposition to Hezbollah. They maintain that Hezbollah must be disarmed and it's military wing dismantled. Armed clashes occasionally occur between especially the LF and Hezbollah. The Free Patriotic Movement led by Michel Aoun is more sympathetic to Hezbollah, and calls for national dialogue and unity. The Free Patriotic Movement belongs to the March 8 Coalition, a group of parties that on a political level cooperate with Hezbollah.
Same goes for the clergy. The country's most prominent Christian leader, Maronite Patriarch Bechara Boutros al Rahi, has called Hezbollah's activities terrorist in the past, and wants Hezbollah to disarm as it is keeping Lebanon hostage. He also wants Israeli aggression to stop, and instead proposes UN intervention to carry out a de-militarization program in the South
If Israel keeps up the pressure and decides to cross the border there is going to be a lot of rumbling in Lebanon.
