He lost the plot years ago, but Ken Livingstone still hasn't lost his party.

On Tuesday night the man whose favourite obsessions, alongside his newts, are offending Jews and mentioning the war, avoided being kicked out of Labour for delivering the ultimate double whammy: claiming Adolf Hitler supported Zionism “before he went mad and ended up killing six million Jews”.

So rather than "Zionara!" it's "see you later!" – a one-year slap on the wrist suspension before the poster boy for British anti-Zionism is inevitably welcomed back to the fold.

Despite the leniency of his sentence, Livingstone was found guilty of all three charges of a breach of rules by the party's National Constitutional Committee. It took three days to decide his words were “grossly detrimental”, giving Ken time to double down, informing reporters outside his hearing that the Nazis also sold guns to Zionists: "So you had right up until the start of the war real collaboration."

He might as well have insisted Eva Braun kept kosher, Heinrich Himmler had a barmitzvah and Joseph Goebbels was a huge klezmer fan.

Ken’s case has hung over his party since April last year, when Bradford West MP Naz Shah was suspended for sharing a Facebook post endorsing the “transportation” and “relocation” of Israelis as a “solution” to the Middle East problem and comparing Israel to Nazi Germany.

She promptly said sorry, but cuddly Ken refused to accept her apology.

With all the timing of a Joey Barton tackle, the man who’s made gratuitously antagonising Jews into an art form saw his opening and dived in with studs showing.

The former London mayor has an unrivalled talent for incurring the Jewish community’s ire, from rolling out the red carpet at City Hall for homophobic Jew-hate preacher Yusuf al Qaradawi to comparing a Jewish journalist to a concentration camp guard. In the latter case a simple sorry would have sufficed but was never forthcoming, so the matter ended up in court. Sound familiar?

Time and again, throughout the course of his chequered career, the veteran leftist has stubbornly refused to back down. He hides behind his record on fighting racism and claims his statements on Israel – whose existence he calls “a great catastrophe” – have nothing to do with his attitude towards Jews.

Livingstone's rhetoric is reminiscent of the dark arts of disgraced Holocaust denier David Irving, wilfully misconstruing history to suit his agenda.

To suggest the tyrant who murdered six million Jews supported a Jewish homeland is like saying the 9/11 terrorists supported the redevelopment of lower Manhattan. In both cases the only intention, from start to finish, was death and destruction. To peddle any other analysis is to lie.

Hitler didn't support Zionists any more than he supported gypsies, gay rights or step-free wheelchair access. He was, however, a big fan of sterilisation, slave labour and slaughter for all these causes.

Livingstone’s idiosyncratic philosophy is old anti-Semitic wine in new bottles. It’s intellectual anti-Semitism masquerading as anti-Zionism. Any fool can deny Hitler’s crimes. It takes a real piece of work to use them against the Jews all over again.

Talking of any fool, former British National Party leader Nick Griffin breathlessly backed Livingstone, tweeting after his initial suspension last year: “One day the world will know that #RedKen was right.” Some endorsements speak volumes.

Jeremy Corbyn can mouth off all he likes about “setting the gold standard for anti-racism”. His party can undertake as many Chakrabarti reports as it wants. But granting members – even the leader’s ideological allies – immunity from moral accountability has now turned the acceptable level of debate on Israel in the Labour Party toxic. Worse still, it has now broken Labour's relationship with British Jews beyond repair.

Richard Ferrer is editor of Jewish News, the UK's biggest Jewish newspaper.