Israel knows it must avoid civilian casualties if it doesn't want the international community, including the United States which is currently reticent on the matter, breathing down its throat. This is not to say that Israel has avoided civilian casualties altogether; they have killed dozens. But they have at least tried to stick to military or economic targets so far.
Let us hope it remains that way. Included among the civilians currently being held hostage within Beirut by the Israeli government (in the sense that they cannot escape the city without endangering their lives) are my two children (aged 8 and 15) and their two cousins (aged 9 and 14), all American citizens, there to visit their Lebanese relatives, along with my children's Lebanese-American father, Lebanese-American uncle, and American aunt. They and millions of innocent Lebanese civilians are caught in the middle of the crossfire, just as the innocent citizens of Haifa, Israel are caught in the crossfire there. It is in no one's best interest for Israel to stop showing restraint.
EDIT: To tell the truth, after today, it doesn't look quite so much as if Israel is showing as much restraint as they could...and should. Do you know how many Lebanese civilians have been killed because of Israel's gung-ho wrecklessness? Do you know how many innocent civilians are being held hostage to their hawkish overreaction? Whether a soldier is beheaded by a Muslim terrorist or an innocent civilian is killed by an Israeli bomb, they're both dead, dead, dead. And right now, there are far more who have been killed by the Israelis than by Hezbollah.
It's unfortunate that you find it so easy to dismiss the lives of people you don't know in a country you've never visited.