Jeremy Corbyn has been embroiled in yet another anti-Semitism row. This time, it’s over his support for an artist whose mural – depicting a shadowy council of Jews – was being scrubbed off a public wall.

The Labour leader has at least admitted he was wrong on this one, for what that’s worth. But as the Jewish Chronicle points out, this is the second Facebook hate group Corbyn has been linked to. To be caught in one may be misfortune; two looks like (at the very least) carelessness.

Notwithstanding the obvious distress this will have caused Labour’s Jewish members and MPs, the story – or the latest update in the story – raises two issues, one about Corbyn and the other about how stories like this get covered and what it says about the normalisation of anti-Semitism in politics today.

First, Corbyn. Despite the long run of incidents connected to the Labour leader it still seems unlikely that he personally harbours anti-Semitic views. Yet over the years they have time and again been put to him or expressed in his presence, whether it be on Facebook or Press TV, and he has a consistent track record of not challenging them.

Option one is that he is simply oblivious to it all, which seems implausible. One or two of the incidents could be explained away on their own – you can just about imagine offering an instinctive defence of artistic freedom without really examining the mural in question, even if you would hope for better judgement from the Opposition’s candidate for Prime Minister. But not all of them.

That leaves the second, more plausible explanation, which is that Corbyn’s approach is that he adopts an attitude of “no enemies to the left”, and refuses to pick fights within the progressive ‘family’ so as not to distract from the more satisfying and much more comfortable business of opposing the Tories, American imperialism, and so on.

Ugly elements of the left have been using that idea has cover for a century – the phrase was coined by Alexander Kerensky, the Russian revolutionary leader, and it gave the Bolsheviks the room they needed to overthrow him. For as long as that attitude prevails amongst the Labour leadership they will never be able to mount an effective resistance to the anti-Semitic (‘anti-Zionist’) elements of the extreme left which have clearly gained a serious foothold in the Party.

Beyond all that, however, is the fact that this latest outrage is simply a much smaller story than it would likely have been even a few years ago. That the leader of one of Britain’s two primary political parties – one bumping along at around 40 per cent in the polls, no less – should be implicated in defending anti-Semitic sentiment ought to be front-page news.

Yet how can it be, when it follows on from so much? As mentioned above, Corbyn was implicated in another racist Facebook group only recently. Before that, what could possibly top the spectacle of a Jewish MP being abused at the launch of Labour’s internal inquiry into anti-Semitism – and the author of that whitewash being handed a peerage weeks later? There comes a point where Labour anti-Semitism isn’t really ‘news’, or at least isn’t new to anyone.

This feeds back into the problem because as press coverage becomes more muted and jaded, the powerful social taboos which help to suppress anti-Semitic sentiment start to erode. If individuals with track records of anti-Semitism can not only survive but thrive within Corbyn’s Labour Party, that sends a powerful signal about what is or is not acceptable and encourages more people to start pushing the envelope with their ‘anti-Zionism’.

Attacking the Labour leader on this can feel futile. Disgusting as many of his past associations are, the public don’t seem to care that he has a history of associating with brutal regimes and terrorist groups. Nor have his critics done themselves any favours with their hysterical reaction to the Czechoslovak spy ‘story’.

But the Tories have a duty not to give Labour a pass on this. Even if much – too much – of the country isn’t paying attention, British Jews deserve to know that at least one of the two parties likely to form a government adopts the zero-tolerance approach which is the only decent response to anti-Semitism. Sajid Javid is right to call Corbyn out – let’s see if he has the courage to respond.