The Greens of the early 2000s made almost a fetish out of not joining in the general nastiness of the House. The party led by Jeanette Fitzsimons and Rod Donald was determined to show New Zealanders that politics did not have to be a blood sport. And, against all the odds, they succeeded. When Green MPs rose in the Chamber there was no invective, no insults, no one-up-man ship.

If they had a question to ask – they asked it. They had a speech to make – they made it. Cooly, calmly, rationally. The rest of the House shook their heads and smiled. This was not how the game of politics was played – not by their teams anyway. And yet, they were quietly impressed by these otherworldly legislators. The Greens certainly were different – but in a good way.

The last representative of that Green Party, its co-leader James Shaw, will soon depart the precincts of Parliament. He will leave behind a very different Green Party from the one that first cantered up the steps of Parliament in 1999. The Green Party of 2024 has become the refuge of zealots. Invective and insult is this Green Party iteration’s stock-in-trade.

The evident respect for reason and science that made the speeches of those earlier Green MPs so effective, has been replaced by the emotive outpourings of people who are so sure they are right that they regard anyone putting forward a different point of view as not only wrong, but evil.

Perhaps the saddest aspect of Shaw’s departure is the well-founded suspicion among political observers that a great many of his “colleagues” will be quietly celebrating. At long last, this suit-and-tie-wearing ambassador of “Green capitalism”; this mild-mannered Cuckoo in the Greens’ nest of fanatics; is leaving. “Good riddance to the cis white male with far too many friends in the National Party” would seem to be the line. “Now, at last, the revolution can begin!”

How many Greens will recall that Rod Donald, naively trusting Helen Clark’s Labour Party not to stab the Greens in the back, invited journalists to join him in picking out the suit (New Zealand-made, of course!) he looked forward to wearing as he joined his fellow ministers around the Cabinet table?

But, then, how certain can we be that even a man of Donald’s infectious sincerity and joviality would be treated with any more respect by today’s Green Party than the shy and self-effacing Shaw? The Green Party’s first co-leader may have been a playful puppy, and its third an introverted cat, but they both suffered under the same incorrigible misapprehension: that who you are should count for more than what you are.

There was a mental and emotional toughness about Shaw that allowed him to face down adversity and cruelty and just keep on going. Both forms of toughness were on display in the weeks that followed the 2017 crisis precipitated by Metiria Turei, Shaw’s co-leader, proudly admitting to committing welfare fraud for the sake of her baby. With the Greens’ poll numbers in free-fall, Shaw, with steely political determination, more-or-less single-handedly hauled his shell-shocked party back over the 5 per cent MMP threshold.

In another time and place, Shaw’s achievement would have made him his party’s darling – but not in the second decade of the 21st century, and certainly not in the Greens. By the 2010s, the foundational goals of the party, born out of the late-20th-century quest for environmental wholeness and social justice, were falling back before the strident demands of Identity Politics.

• Bruce Cotterill: The Christchurch call and the end of Woke
• Muriel Newman: 2024 – a Year of Reckoning
• ACC told to reconsider woman’s injury claim after suicide attempt linked to medication

Paradoxically, Shaw’s 2017 success unintentionally reinforced the positive values of masculinity: courage, steadfastness and self-discipline. What’s more, these had prevailed where the feminine virtues articulated by Turei had brought the Greens to near collapse. Even worse, Shaw was white and Turei was brown. The party might have been saved, but it had been saved by the wrong sort of person. A cis white male, doing what cis white males do. Shaw wasn’t a hero, he was an embarrassment.

And then he had the temerity to shepherd the Zero Carbon Bill through the House of Representatives. Against the odds, he succeeded in committing his country to the climate goals laid down in Paris. Once again, his party might have been expected to treat him as a hero, but, once again, his party contrived to feel embarrassed.

Shaw had struck a significant local blow against global warming, but the way he had done it was all wrong. He had reached out to the other parliamentary parties, arguing successfully that if there wasn’t a broad, cross-party determination to resist climate change, then any legislative triumphs could only be short-lived. In pursuit of consensus, long promoted by the Green Party as the epitome of “appropriate decision-making”, Shaw was prepared to compromise. That’s how the Zero Carbon Bill became the Zero Carbon Act.

But, that legislation, Shaw’s proudest legacy, also represents a comprehensive refutation of the political style being perfected by the rest of the Green Party – its female co-leader in particular. Because, Shaw saw no benefit in glueing his hands to the roadway, or hurling soup over priceless works of art; his preference was quiet and respectful dialogue.

He did not earn the respect of Todd Muller and Simon Bridges by wearing a keffiyeh and chanting slogans, but by searching for the concessions that make unity possible. In short, Shaw rejected the performative politics of his colleagues in favour of the realpolitik that gets results.

And they hated him for it. The patience and forbearance of Shaw, as his party’s fanatical factions castigated and humiliated him for all the world to see, were surely the best arguments for the rest of his party coming to his rescue and reaffirming his co-leadership – which they did.

But not before changing the party’s rules to make the future election of a cis white male to the Greens’ co-leadership a near impossibility. The wonder is not that James Shaw is finally leaving the Greens: the wonder is that he has stayed with them so long.

And what of Shaw’s presumptive successor, Chlöe Swarbrick? There was a time when this youthful political prodigy held out the hope that Jeanette Fitzsimon’s cool intellectual style might outlive her. That her torch of reason may have passed to a new generation.

Certainly, Swarbrick’s first few years in the House were distinguished by a forceful, yet respectful, debating style, supercharged by her impressive mastery of the facts. Of late, however, Swarbrick’s torch has flared and sparked wildly – causing observers to wonder whether she should have – or even wants – the job.

Patience and forbearance, respect, and the willingness to compromise: the qualities that James Shaw brought to his co-leadership of the Green Party may turn out to be the only qualities that can save the planet. It will be a genuine tragedy if they leave Parliament with him.