The UN has passed 3 separate resolutions (in 1978, 2004, and 2006), telling Lebanon to get all non-state militias out of the south, and away from Israel.

Lebanon had decades to stop these armies from attacking Israel from within their borders.

They chose not to act.

So, Israel is doing what any Western nation would have done decades ago.

It largely was uninhabited. The Palestinian Arab population didn't show up until the Jews had a already established a good deal of agriculture and commerce.

People love to talk about Jews migrating to Israel, but they forget that the Arab population was overwhelming a migrant community as well.