Editor's Note: (John McTernan is head of political practice at PSB, a strategic research consultancy. He was a speechwriter to ex-British Prime Minister and Labour Party leader Tony Blair and was communications director to former Australian Prime Minister Julia Gillard. The opinions expressed in this commentary are his own.)

(CNN) The UK's official opposition, the Labour Party, "is a moral crusade or it is nothing." Those are the words of Harold Wilson, one of the Labour Party's most successful Prime Ministers, and they should be ringing in the ears of its current leader, Jeremy Corbyn.

The moral superiority of the left is often mocked as political correctness, but it is rarely questioned. But the resignation of Luciana Berger and six of her colleagues has brutally and publicly done exactly that.

When Berger said that she had come to the "sickening conclusion" that the Labour Party was "institutionally anti-Semitic," she ripped open a conflict that is tearing the UK's main opposition party apart.

Brexit is too often the only prism through which British politics is seen. The minute details of alternatives to the "backstop", the ebbs and flows of cross-party and intra-party alliances, and parliamentary procedures dominate discussions. It has all, in the end, been a story about Theresa May, her government and her authority.

Meanwhile, very little attention has been given to the very real crisis within the Labour Party.

This week's resignations may have Brexit as the backdrop, but that was not the cause of the rupture. This split has happened because of how totally successful Jeremy Corbyn's hard-left takeover of the Labour Party has been.

The charges laid by the now independent lawmakers were powerful -- a culture of bullying, fears for national security, profoundly anti-business policy positions -- and they all come from the very top. They are a feature of Corbyn's leadership, not a bug.

That's why this split seemed both so inevitable but also so futile.

It had to happen because it seems there is no chance that Labour will tackle anti-Semitism properly under its current Leader. That was seemingly made clear when Labour's General Secretary, Jennie Formby, published the details of the action, or rather inaction, on investigated cases of anti-Semitism.

Though the evidence about Corbyn's priorities -- from defending anti-Semitic murals to wreath-laying in Tunisia -- had been hiding in plain sight all along.

But it never damaged his standing with the party's membership, because it is part and parcel of his fundamental appeal as a politician. His defining characteristic is his consistency: he came to his views in the 1970s and has never found a need to change them. Corbyn, of course, denies any suggestion that he has been soft on anti-Semitism and consistently reminds people that he opposes all forms of racism.

These resignations don't threaten Jeremy Corbyn's control over the Labour Party because they confirm his appeal rather than confronting it. Corbyn may have alienated seven of his MPs, but he was being authentic and true to himself.

The truth is -- that like much in politics globally in 2019 -- Labour's leader is a symptom, not the cause.

The Global financial crisis continues to shape our world. It is driving the populist revolts that can be seen in the politics of Italy, France and the United States.

The turn to populism takes many forms, but it nearly always strong nationalist and statist strands.

Labour's commitment to large-scale nationalization of industry shares this in common with US President Donald Trump's plan to build a wall -- both are massive gambles on the ability of the Big State to deliver.

This is the paradox of Labour's current position. The criticism made eloquently by Luciana Berger and Chris Leslie is unanswerable. An antisemitic, anti-business Labour Party led by a man who they believe gives Russia the benefit of the doubt over the poisoning of British citizens, cannot -- indeed should not -- take power. Yet, the forces that propelled Jeremy Corbyn in his takeover of Labour are still all there.

A new political movement needs a great cause as well as genuine grievances. The banal boilerplate of the Independent Group's website are not that. Politics is about inspiring ideas for the future. And at the moment, whether you like it or not, populists like Jeremy Corbyn are doing that better than any centrist.