It is the curse of every democratic socialist movement in history. For the ultra-leftist, the real enemy is not the right wing of politics – which in British terms means the Tories.
Before the revolution gets round to destroying them, somewhere in the indefinite future, it is first necessary to rout the revisionists of the mainstream left (i.e. Labour). The most effective method is from within rather than by shouting from the fringes.
The permanent duty of democratic socialist parties is to remain alert to this danger for the consequence of carelessness, or excessive tolerance, is to make them unelectable and of not the slightest use to the people they are supposed to represent.
None of that is to dispute the legitimacy of debate within a party like Labour, covering a spectrum of opinion from pretty far left to centre on every issue under the sun. The distinguishing feature of ultra-leftism is its contempt for electability.
In 2015, debilitated Labour walked into that historic trap. The leadership of Ed Milliband was a disaster, itself created out of factionalism without regard for consequences; then compounded by the open-door to membership at three quid a head and the vacancy he immediately, selfishly chose to create.
Gnarled old Trots who had been marginalised from the 1980s and trade union barons with Scouse accents could hardly believe their luck. They had been handed the keys to the kingdom and all they needed was a front-man to open the gates.
Step forward Jeremy Corbyn. It might have been any one of half a dozen from among the usual suspects but it was his turn to go through the motions of standing for leader. Except this time, by accident of history and timing, it was for real.
It would be unfair to describe Jeremy as an ultra-leftist which implies some coherence of ideology. Rather, he was a permanent oppositionist who had spent a comfortable political lifetime hob-nobbing with every demagogue who passed through Islington.
The best that can be said in his favour is that he never aspired to being leader or, I guess, wanted to be. He was not a bad person – which is more than can be said for some of the rabble he brought in his wake.
That is where anti-semitism comes in. Pre-Corbyn, I had never heard the words “Labour” and “anti-semitism” in the same sentence. It was anathema – one of the great moral crimes of history. In contrast, it was no stranger to the garbled theories and paranoias of ultra-leftism.
I do not believe this was some great plague which afflicted the whole Labour Party any more than I think Corbyn was personally anti-semitic. But the failure to acknowledge that an evil had been created and must be rooted out made him complicit.
Corbyn was incapable of leadership, particularly if it involved taking on people he was involved with for decades or the strong, destructive wills in his dysfunctional inner circle. Of course the issue was talked up by opponents as well as by the genuinely aggrieved, but what did he expect?
Predictably, the Corbynite tide receded as fast as it came in. Most who were caught up in it will have moved on to other hobbies, the fate of Labour the least of their interests. Corbyn’s legacy is Boris Johnson as Prime Minister with a Tory majority of 80 and a Labour Party stained with the EHRC conviction.
There is now a credible leader and a force capable of winning elections, but these things do not happen overnight. Meanwhile, Corbyn cannot bring himself to apologise while McCluskey threatens “chaos” which I doubt he will be able to deliver. That ship has sailed.
A necessary line has been drawn and apologies offered to those most directly hurt by this revolting episode in Labour’s history. But the other apology due is to the millions for whom Labour governments are a necessity for hope rather than an optional extra for political thugs and dilettantes.