THERE IS REALLY only one thing to be said about the unrest and violence flaring in southern Lebanon, where Israeli troops are under continuing fire from the local people and now from units of the Lebanese army, not commonly known as much of a fighting force. The Israelis should get out. They got a welcome from many Lebanese in 1982 for ousting the PLO and for offering a kind of partnership to the Christians, but they have worn out that welcome and are now regarded simply as an occupying force. They have no legitimate business in Lebanon beyond ensuring the security of their northern frontier.

In February the Israeli forces pulled out of Sidon and environs in what was intended to open a careful three-stage withdrawal. The working theory was to reduce the ratio of hostile Shiite oslems and Palestinians in the population under occupation. But the Israeli forces found themselves abandoning a natural line at the Awwali river for a more exposed position, and Shiite actions have increased. Some Israelis now fear that this particular terrorism will follow them back into Israel proper. Meanwhile, the resistance intensifies, producing harsher retaliation, more terror and new casualties: the familiar cycle.

Why does Israel withdraw so slowly? Partly because of the reluctance of Likud, which was responsible for going deep into Lebanon in 1982, to acknowledge the need to cut Israel's losses now that the party shares power with Labor. To other Israelis, however, it is apparent that to drag on in Lebanon is to play into the hands of the Syrians and others who see a profit in having Israel bleed. By staying on, moreover, Israel creates new friction with the United Nations, whose peacekeepers and diplomatic auspices it needs to cover its continuing withdrawal.

Israel had thought to leave behind friendly Lebanese. But since the Israeli occupying forces left Sidon, Shiites and others have been killing and intimidating those friendly Lebanese. As its last line of defense of its territory, Israel will have to rely on forces stationed on its territory.

This will leave southern Lebanon to the Lebanese: to the army and government, which are making a last-ditch effort to gain prestige by becoming patrons of Israeli withdrawal, and to the communities and their militias, which, freed from the Israeli distraction, are having to face the full consequences of their own poisoning rivalries. It is not a pretty picture, but it is Lebanon's. It is Lebanon's, that is, unless Syria can actually play the pacifier's role it is always claiming and help to settle Lebanon down.