The day after October 7th, Israel was attacked from Lebanon. Israel has every right to do what it is doing to secure its northern border. Any country on earth would do the same.
Hezbollah at least recently was much stronger than Lebanese army and even nowadays Lebanese army afraid to challenge Hezbollah. Concept of a powerful non state actor is something many people in the west refuse to acknowledge.
Mainly because Lebanon is a failed state with arguably non state actors (Hezbollah being an Iranian proxy) doing the "defending". Which is not real defending but pestering Israel with attacks and drawing more punitive action.
It's a country with two power centres and two national armies. Thus, "divide and rule" politics works exceptionally well there and no one should be surprised their lack of political unity is working against them. While the Lebanese army has no love for the Israelis they are acting under US pressure and advise to not get involved as Hezbollah is taking the brunt of the attack, which the US and some Lebanese political actors hope will hope weakens it enough and eventually lead to its merger / absorption. It's an idiotic way to think of, ofcourse, because there is no guarantee that the US and / or Israel are likely to stop the war (or their ethnic cleansing / genocide), or stop making political demands on Lebanon once the Hezbollah is gone. The loss of Hezbollah fighters will mean Lebanon's military actually becomes weaker.
They're not defending anything, not even their families. They're only struggling in an ideological war. Randomly firing missiles at Israeli civillians and drawing punitive action from Israeli leadership, which is all too happy for another reason to blow them up and invade.
Hezbollah, whatever you may think of them, are the main security actor in the South. Why should they not defend their civilian population?