The Crisis of Zionism was a phenomenon when it was published just four years ago. American journalist Peter Beinart's provocative thesis was that the younger generation of American Jews is increasingly alienated from the Jewish state, because Israel's policies regarding the Palestinians clash with their liberal-democratic ideals.

While many reacted furiously to the implication Israel was illiberal, his central point - that young Jews on the left tend to be less connected to Israel than are their elders - has sparked much more thoughtful debate, because it appears to be backed up by several surveys. Unfortunately, Beinart's book is a red herring. It may be true that some diaspora Jews are deeply conflicted about Israel's treatment of the Palestinians and what they see as an erosion of Israel's democracy. But that is not what poses the greatest threat to Israel-diaspora relations.

That threat comes from dismissive, contemptuous and downright rude attitudes Israeli politicians and religious leaders display towards non-Orthodox Jews and even, on occasions, diaspora Modern Orthodox Jews.

Over the past few months alone, we've had Religious Services Minister David Azoulay, of the ultra-Orthodox Shas party, explaining that he "can't permit" himself to call Reform Jews Jewish. Israel's Ashkenazi chief rabbi, David Lau, has opined that a visit by another minister to a Conservative school in New York was "unacceptable to the Jewish People". Now Likud's tourism minister, Yariv Levin, has decided that Reform Jews will "be all but gone in three generations".

Meanwhile, the rabbi of the Western Wall has just won a battle to prevent Reform, Conservative and Modern Orthodox women from praying by the Kotel with a tallit or a Sefer Torah - although that is seen as a fundamental right by much of diaspora Jewry. Diaspora conversions are routinely dismissed, and Israel recognises the conversions of only a tiny handful of American Orthodox rabbis.

Here in the UK, where the Progressives are a minority of our 300,000-strong community, this affects relatively few people. But Reform and Conservative Jews make up more than half of America's six million Jews, and the Orthodox are just 10 per cent.

So why do Israel's representatives take this attitude? They are ignorant of the last 200 years of Jewish history. They apparently still regard Reform and Conservative Jewry as fleeting, insignificant side-shows. They don't care, because they believe that Reform, Conservative and Modern Orthodox Jews are inferior. And they are allowed to by the ruling Likud party, which has cynically delegated responsibility for religious matters to Charedim, who have held the balance of power in successive coalitions.

Either way, to diaspora Jewry, the message could not be clearer: "We don't really consider you Jews".

Why, then, should diaspora Jewry care about Israel?

For your average diaspora Jew, this is a far more emotive and hurtful issue than Israel's policies regarding the Palestinians, because it's not just a clash of values. They - we - are being personally rejected and dismissed.

It is an enormous misjudgment on Israel's part.

The diaspora still looks to Israel for inspiration and sees it as representing the centre of Jewishness and Jewish life. But if Israel wants to continue styling itself as the homeland of all Jews; if Israel wants to continue receiving political and financial support from the diaspora, it needs to show some basic understanding of, and respect for, the people concerned - not continually insult them.

Special as this relationship is, it will not withstand one partner being metaphorically spat on by the other.