One of the personal downsides of defeat as an MP is immediacy. You make a speech in the middle of the night from a packed stage to a largely empty hall. Each word is offered from behind a fixed smile as you pretend to be delighted that someone else will be leaving with the job that you arrived with. For weeks afterwards friends talk to you as though you’ve suffered a terrible illness, whispering their best wishes for your full recovery.

Others simply keep out of your way. But over the Christmas period I met up with some of those I hadn’t seen since that election night. Among them was an old friend, John Arthur, a lovely gentleman in his nineties. He has been a Labour member since ­before the NHS, the State of Israel or my dad were born. Years ago I presented John with his Veterans Badge as a small thank you for his time in national service.

He’s a kind optimist and an elder in the local church. But he seemed unusually unsettled. I asked him about his health, his family and all the other things that could be causing his anxiety, but each of the obvious inquiries met with a pretty contented reply. It was only when we turned to politics that I got closer to the truth. And it’s why I’m writing this column. Sheepishly, John told me that he was thinking of cancelling his 70-year-long membership of the Labour Party. He no longer recognised the party that he had lived most of his life in.

This from a man who used to collect the annual membership fees of half a crown by cycling from one party member’s house to the next. He has never sought attention from anyone or election to anything. He is the type of proud, working-class patriot who has kept the Labour Party alive. One of his happiest memories was shaking the hand of Aneurin Bevan at the Glasgow May Day rally in 1951. And now, in the tenth decade of his life, he felt like a stranger in his party.

John doesn’t do Twitter but if he did he would be traduced by some loudmouths as a Red Tory. It is little comfort that many of these keyboard warriors count their Twitter following in the dozens and their attachment to the Labour Party in months.

I can only share with others what I said to John, which is that the Labour Party has been nurtured for over a century. It is as much his party as anyone else’s and what he has helped build with patience he shouldn’t abandon in haste. After all, we elect a leader, not a monarch, and no one person has ever owned Labour. Surely John has earned the right to have his criticisms welcomed.

A party whose mottos include “Unity is Strength” has rarely entertained the politics of energised internal intolerance. Lots of really decent people have recently joined Labour and they are part of a party that from its earliest days has lived with our fault lines. At the first ever meeting of the Parliamentary Labour Party in 1906, Keir Hardie and David Shackleton tied 13 votes each in the election for PLP chair. Few leaders have mistaken debate for division.

Of course, it would be charitable to look now at Labour’s leadership team and see only the velvet glove of north London dinner-party politics rather than the vengeful iron fist of the Momentum faction – especially with the latter having a far clearer plan than the fabled former. We are also told that our current leaders are principled and harmless. But those leaving Labour see little that is harmless in consciously giving up the centre ground to the Tories, or principled in handing the centre left to the Lib Dems. It all means that, for the first time since 1952, an incumbent Tory government has entered a new year further ahead in the polls than it was at the previous year’s general election.

I know that for John and others “Not in My Name” can be a powerful slogan but it is rarely a strategy. In fact, when it comes to resigning from Labour, the opposite is likely. Jeremy Corbyn won the leadership fair and square but it’s worth remembering that, among those who were members at the general election and even a month afterwards, he didn’t win a majority. I mention that fact not out of denial, but as a reminder that there are tens of thousands of people just like John – who believe in Labour as a party of principle and as a credible alternative government. Crucially, they are backed by all but 16 Labour MPs.

They know that the very worst day in government is immeasurably better than the best day in opposition. Despite the passionate leadership of the likes of Hugh Gaitskell, Michael Foot and Neil Kinnock we have never immortalised the huge social reforms of opposition. Why should we, when they’re called the poll tax, three million unemployed and the bedroom tax?

However, my appeal to moderates to stick with Labour isn’t a crude argument about the balance of forces in any future leadership contest. Instead, it’s a sense of what we can still achieve and all that we have shared; the pride in what we have built together, the hurt of our frequent defeats and the satisfaction in the lives changed by our occasional victories. Remember with affection Clement Attlee as deputy to Winston Churchill who built the NHS and backed nuclear armament; Harold Wilson who opened the Open University and kept Britain out of Vietnam. And yes, Tony Blair, who brought us the minimum wage and strengthened peace in Northern Ireland.

Finally, turn Marx on his head; the other one, that is – Groucho. He famously opined: “I don’t want to belong to any club that will accept me as a member. Please accept my resignation.” Instead, join thousands of others and vow: “I believe in the timeless cause of Labour. I’m going nowhere. Please accept my determination.”