Whatever your view of Diane Abbott, or your view of Keir Starmer, there has plainly been a serious blunder in Labour’s campaign when her treatment ends up leading the BBC news coverage and splashed across most front pages. Quite apart from the bad look, Labour’s big NHS day was blown away by a story on the fate of one MP. First, remember this. Starmer has pulled off the near-impossible in a remarkably short time: returning Labour to electability after its worst crash in living memory. This miraculous recovery has required unflinching severity in dealing with antisemitism and a resolute “Labour has changed” message after Jeremy Corbyn’s leadership. It was risky to expel the former leader – but he was extraordinarily lucky that Corbyn, with characteristic obstinacy, chose to rule himself out by refusing to accept the overall verdict of the independent Equality and Human Rights Commission (EHRC). Had he accepted its judgment and offered a sufficient apology, he would probably still be a thorn-in-the-side Labour MP. If he wins as an independent, that’s a very minor embarrassment as Labour sweeps to power. Diane Abbott, a longtime Corbynite, did rapidly apologise last year for writing a letter to the Observer comparing Jewish people’s experience of racism with prejudice against gingers, then accepted the public embarrassment and completed a two-hour online antisemitism awareness course. There it should have ended, instead of 15 months of “investigation” by Labour high command. The Labour whip was restored to her this week, but she says she has been told that she cannot stand for Labour in the Hackney North constituency she has represented for 37 years. Starmer appearing on TV, denying it was up to him and giving no reason for the interminable delay, lacked honesty – and it showed. Of course he’s in charge. He should have stepped in immediately and let her candidacy be announced, end of story, moving on to what matters: chasing out these Tory degenerates. Until now, he has brooked no diversions from the business of winning, which from his first day has been his prime purpose. This concerns his authority and his self-confidence. That he was elected leader, not Rebecca Long-Bailey, showed Labour was ready for change, even if he has since walked back or altered pledges after the financial traumas of Covid and the cost of living and energy crises. As prime minister to be, he and his team bestride the political scene, so eliminating one or two minor irritants on the fringes of his party should be beneath his dignity. It may be a sign of inexperience. Tony Blair had the full-blown self-confidence to largely ignore his leftist rump. Ah, say some Labour MPs, what if we were to win by one or two seats, and the likes of Diane Abbott, Lloyd Russell-Moyle and Faiza Shaheen (both leftists also removed from standing at the last moment) were to hold sway? There are reasonable objections to Shaheen being the best candidate to represent Chingford and Woodford Green, and Russell-Moyle can be infuriating, but these last-minute evictions are demeaning to Labour’s grander horizons in this epochal moment. Demanding absolute discipline on every issue looks like weakness. It makes Labour’s commitment to serious devolution look somewhat improbable – control freaks can’t let go. (I have my doubts as to whether they should devolve too much. Wait until it gets to devolving money and power to the likes of Tory Kent and Buckinghamshire, when their priorities are grammar schools, not new Sure Starts.) Abbott is a “trailblazer”, Starmer has said. The Tories constantly mock that photo of him taking the knee for Black Lives Matter. That signified his genuine understanding of how deeply race still blocks the chances of so many. Doing something about it means encouraging those who overcome obstacles. For many young black women, Abbott’s story is indeed that of a trailblazer, the word Sadiq Khan also uses in praise of her. While on the fence over her candidacy, he recalls how seeing her in 1987 “made a huge impact on me”. It’s easy now to forget how the arrival of a young black woman – struggling always as the only black girl in her grammar school, the only one in her Cambridge cohort – transformed possibilities for so many. She pays the price in never-ending disgusting abuse, as when the biggest Tory donor said she “should be shot”, without Rishi Sunak casting him off. MPs do get murdered. That alone is a reason why Labour should stand by her. Acknowledging her iconic role in the party’s history, and forcing the Tories to diversify too, is far more important than some of her jarring views. True, Abbott’s seat has the fourth largest Jewish population in England and Wales, many of whom will have been profoundly offended by that awful letter to the Observer. In the left’s off-piste diversion into identity politics, away from collective solidarity, this ranking of degrees of victimhood destroys its core purpose. Badly miscast as shadow home secretary, Abbott gave car-crash interviews in the 2019 election that were an excruciating factor in Labour’s collapse. But all that really is beside the point. Across the party, many “Blairites” are shocked at her mistreatment. It’s a fast-moving story. Perhaps Labour campaign leaders will come to their senses, Starmer will see how petty this looks against the epic importance of this election and Abbott will be reinstated. Once Labour is in power, losing support from liberal-left and green-inclined voters will be an increasing threat. Beware of alienating them pointlessly. Polly Toynbee is a Guardian columnist