The Labour Party’s leadership has said it will bring “action” against Margaret Hodge for calling Jeremy Corbyn an anti-Semite and racist after the party’s ruling National Executive Committee voted not to include the full IHRA definition of anti-Semitism in its code of conduct.

If there is ever a moment that provokes an organised rupture by Labour MPs – rather than the odd and situation-specific explosion such as John Woodcock's exit – it will be if the Labour leadership doesn't back down.

It's worth pausing to appreciate the scale of the unity that Labour’s position has provoked in the Jewish community. To give you an idea, here are some of the things that the 68 rabbis who signed a letter of protest against the party's actions disagree on: the literal truth of the Torah, the creation of the state of Israel and whether all of the 68 signatories really count as rabbis, to name just three. Yes, no community thinks in one mind but this is as close to unanimity as you could ever want to achieve.

The principle that a minority group has the right to define its own oppression is one reason why Labour MPs are so uneasy. But the other, and perhaps more important factor is this: Corbyn has expended more political energy on defending the party's stance on the IHRA than he did on opposing the expansion of Heathrow, which he believes to be an environmental calamity. It shatters their ability to believe that when they disagree with the leadership over anti-Semitism it is the result of error or foolishness on their leader's part, which makes it harder for them to stay.

They know, too, that their power to change anything within the Labour party is non-existent. They have just three representatives on the party's NEC and the blunt truth is the last real choice that Labour MPs made was on 15 June 2015 when they put Corbyn on the ballot. The question Corbynsceptics grapple with is whether they are better off retaining their seats in parliament, where they can shape a Labour government's legislative agenda even if they cannot shape its policy platform, or if they should break away and attempt to win as part of some new force.

What all Corbynsceptic MPs know is that the trade-off is not straightforward and they have no way of knowing which strategy they ought to pursue. But if Labour’s disciplinary processes are brought to bear on Margaret Hodge, for many of them, the question will no longer be one of strategy but of morality.