In the summer of 1947 a semi-derelict 200-berth Chesapeake Bay steamer carrying 4,500 Holocaust survivors, renamed the Exodus, set out from France to run the British blockade of Palestine. The survivors had been rotting in displaced persons camps since the end of the war, waiting to find a country that would take them. The organisers of the expedition, the Zionist movement, were operating a policy of illegal immigration as both a humanitarian rescue operation and as a calculated move to politically gerrymander the country's Jewish population. They didn't expect to be able to land, but they knew that the rickety vessel with its pitiful human cargo of refugees would show up the British as cold-hearted colonial masters. The Exodus could equally have been called End of Empire.

As the ship approached Haifa, the commander received a radio signal from the Zionist leadership not to risk the lives of the passengers by a confrontation. But the incalcitrant Polish captain refused to turn back. Hemmed in by three British destroyers, the crew and passengers found themselves boarded, and retaliated with whatever weapons came to hand – a consignment of cans of kosher corned beef. The British killed three people, one bludgeoned to death by a rifle butt in the face. A few days later the passengers were transferred to another ship and sailed back to Germany, back to the refugee camps, under withering press headlines: "Return to the death land," read one.

The gripping events in the eastern Mediterranean, shown on the news reels, evoked massive public sympathy, particularly in America where Britain was seen as the old colonial regime. The media coverage was a PR catastrophe for Britain. To the ship's captain, Ike Aronowitz, when I met him in 2007 shortly before his death, Ernest Bevin's decision to repel the Exodus was a gift from a God who had "sent us Ernest Bevin to create a Jewish state".

Against the single image of a ship full of Holocaust survivors being beaten by squaddies, the British had to set a complex narrative, too complicated for a public looking for a simple story of victims and oppressors. The British spoke of the needs and wishes of the existing Arab population of Palestine; a new Jewish state implanted in the Middle East against the will of its native inhabitants was not to be the happy ending of a tragic Jewish story. Yet the Exodus was to be instrumental in cementing support later that year for the UN partition vote which divided Mandate Palestine, and the largely erroneous novel and film of the same name in the late 1950s would create a lasting mythology. The image of the boat had greater power than the warnings from the Foreign Office or the pleas of Arab leaders.

The events early this week of the boarding of the Gaza aid flotilla should have jogged the memories of Israel's political leaders and its military. The sight of Israeli politicians, diplomats and army spokespeople trying to assert a more complicated story than that of innocent civilians brutally murdered by an act of piracy has not washed with the public. No amount of showing videos of the peace activists attacking the abseiling Israeli soldiers will answer the question: what were the soldiers doing there in the first place and why would the passengers not defend themselves against their attackers, exactly as the refugees had done in 1947?

Israel's political reasoning, of a Hamas-controlled Gaza strip, of the threat to the Jewish state from Gaza in the south and Hezbollah in the north, backed by the nuclear-ambitious Iran, falls on deaf ears. Legal arguments by maritime experts that Israel was within its right to assault the ship in international waters can't compete with the authoritative presence on another of the vessels of the internationally bestselling novelist Henning Mankell, who risked his own life to bring aid to the starving millions of Gaza.

Palestinian solidarity movements have not, until now, attained the critical mass of the campaign against apartheid South Africa. Perhaps, like the Exodus in 1947, the Gaza aid flotilla will be the tipping point in the long agony of the Palestinian people, when wavering public opinion finally turns decisively against Israel and the whole Zionist project of a national home for the Jews.

When public sympathy is outraged by what has been described as a massacre, the fine points of what is to be the solution to the rival claims of Arabs and Jews for the same piece of territory are not the point. We look back on the ship Exodus and wonder if our parents and grandparents should have thought harder and emoted less. But emotions are what you feel, you cannot help it. Human empathy for the inmates of a vast open air prison undergoing collective punishment will always trounce the warnings of the thinktanks. The image of the Gaza flotilla has etched itself on the mind, whatever the unforeseen consequences of our collective outrage.