What is amazing is that so many Western leaders, so many presidents and prime ministers and, I fear, so many editors and journalists, bought the old lie; that Israelis take such great care to avoid civilian casualties. "Israel makes every possible effort to avoid civilian casualties," yet another Israeli ambassador said only hours before the Gaza massacre. And every president and prime minister who repeated this mendacity as an excuse to avoid a ceasefire has the blood of last night's butchery on their hands. Had George Bush had the courage to demand an immediate ceasefire 48 hours earlier, those 40 civilians, the old and the women and children, would be alive.

The Sabra and Chatila massacre was committed by Israel's right-wing Lebanese Phalangist allies while Israeli troops, as Israel's own commission of inquiry revealed, watched for 48 hours and did nothing. When Israel was blamed, Menachem Begin's government accused the world of a blood libel. After Israeli artillery had fired shells into the UN base at Qana in 1996, the Israelis claimed that Hizbollah gunmen were also sheltering in the base. It was a lie. The more than 1,000 dead of 2006 – a war started when Hizbollah captured two Israeli soldiers on the border – were simply dismissed as the responsibility of the Hizbollah. Israel claimed the bodies of children killed in a second Qana massacre may have been taken from a graveyard. It was another lie. The Marwahin massacre was never excused. The people of the village were ordered to flee, obeyed Israeli orders and were then attacked by an Israeli gunship. The refugees took their children and stood them around the truck in which they were travelling so that Israeli pilots would see they were innocents. Then the Israeli helicopter mowed them down at close range. Only two survived, by playing dead. Israel didn't even apologise.

Twelve years earlier, another Israeli helicopter attacked an ambulance carrying civilians from a neighbouring village – again after they were ordered to leave by Israel – and killed three children and two women. The Israelis claimed that a Hizbollah fighter was in the ambulance. It was untrue. I covered all these atrocities, I investigated them all, talked to the survivors. So did a number of my colleagues. Our fate, of course, was that most slanderous of libels: we were accused of being anti-Semitic.

Yes, Israelis deserve security. Twenty Israelis dead in 10 years around Gaza is a grim figure indeed. But 600 Palestinians dead in just over a week, thousands over the years since 1948 – when the Israeli massacre at Deir Yassin helped to kick-start the flight of Palestinians from that part of Palestine that was to become Israel – is on a quite different scale. This recalls not a normal Middle East bloodletting but an atrocity on the level of the Balkan wars of the 1990s. And of course, when an Arab bestirs himself with unrestrained fury and takes out his incendiary, blind anger on the West, we will say it has nothing to do with us. Why do they hate us, we will ask? But let us not say we do not know the answer