It started in France in 1894, when a Viennese journalist covered the Paris treason trial of Captain Alfred Dreyfus. "In Paris, as I have said, I achieved a freer attitude toward anti-Semitism," Theodor Herzl wrote in his diary. "Above all, I recognised the emptiness and futility of trying to 'combat' anti-Semitism." That futility led him to propose an escape from anti-Semitism to a nation-state in Palestine.

nti-Semitism has returned to France with the murders at a Jewish primary school in Toulouse of a teacher, his two young children and a third child. The killer was a small-time hoodlum-turned-jihadist named Mohamed Merah, who told police during their 32-hour siege of his apartment that he was avenging the killings of Palestinian children by Israelis.

Merah's crimes were more complicated, as he had in the previous days killed three French paratroopers who, like him, were Muslims of North African origin. Their murders were Merah's protest against the French military presence in Afghanistan. His other claim to police was that he wanted to bring France "to its knees".

France has not been brought to its knees, and Merah has done the Palestinians only harm. Few would have predicted in 1895, when Herzl was writing The Jewish State, the lasting harm of his solution to what he called "the Jewish problem". In 1948, three-quarters of the indigenous population of Palestine were expelled. The refugees still live in the wretched camps of Lebanon, Syria, Jordan, the West Bank and Gaza. Israel banished thousands more in 1967 and, ever since, has demolished houses and seized land to achieve what the Palestinian scholar Edward Said called its goal of "more land, fewer Arabs".

Herzl's solution to one problem created another, but the root causes of both were the same: not a "Jewish" problem, but anti-Semitism itself. Where anti-Semitism flourishes, Jewish communities will understandably consider the option of emigration to Israel. The Israeli state offers immigrants subsidised housing and other benefits that make settlement in the occupied West Bank a more attractive option than buying an expensive flat in Tel Aviv.

As a result, Palestinians lose their farmland and livelihoods. This is no secret in Israel, the territories or abroad, where the US taxpayer funds the land-theft and dispossession process. Why, then, do so many who claim to support justice for the Palestinians succumb to the virulent anti-Semitism that is the cause of their woes?

Those who daub swastikas on synagogues, desecrate Jewish graves, taunt Jewish children in schools and exclude Jews from their clubs commit crimes against Jews and Palestinians alike. The demagogues and militants who make Jewish people outside Israel feel insecure force them to consider the option a majority of them have until now rejected: moving to the Jewish state and, possibly, settling on land stolen from Palestinians in the occupied West Bank.

When Salim Fayyad, the nominal prime minister of the non-state that is Palestine, condemned Merah's murders, it was in the interests of Palestinians. "It is time for those criminals to stop exploiting the name of Palestine through their terrorist actions."

A previous Palestinian leader, Haj Amin Husseini, did his people no favours by taking Hitler's side in the Second World War in the perverse belief that Palestine's Arabs faced a threat from the Jewish people rather than from the anti-Semitism that drove them out of Europe. Until the mid-20th century, the Muslim world took pride in the Ottoman invitation to the exiled Jews of Reconquista Spain to settle in its Arab dominions. There, they were welcomed and often flourished.

Zionism had never taken root in Baghdad, Yemen, Morocco and the other centres of Judaic culture in the Arab world. After Israel was established in 1948, the Arab regimes, like Merah, took revenge on the blameless by expelling their Jewish citizens. Sephardic and Iraqi Jews gave the new state the demographic ballast it needed to fill the towns and villages emptied of their Palestinian inhabitants. It was an own goal that hurt both the Palestinians and the Arab world's Jews, who lost their homes and wealth.

In Toulouse's Place du Capitole last Friday, more than 4,000 people honoured the innocents who were shot by Merah. The participants, like the victims, included French people from Jewish and Muslim backgrounds. Pierre Cohen, the Socialist mayor, told them: "Toulouse, this is not us … because Toulouse is a world of welcome, a world of generosity."

Unlike in the days of Dreyfus, when Anti-Semitic Leagues formed in France, Merah's killings have engendered mass support for France's Jewish population - including from the country's most prominent Muslim leaders. Things have changed since Herzl's time, even if killers like Merah make it hard to convince those whose children, fathers and husbands are dead.

With champions like Mohamed Merah, the Palestinians' enemies can relax.