I watched the video with some trepidation. Stonewall (the campaigning gay and lesbian equality organisation) had just sent me the YouTube link. This was to a short film of the dinner that Stonewall’s founders attended last year to celebrate the quarter-century anniversary of our existence; and most of us had been there. Now we were but wrinkled reminders of the young revolutionaries we had once been.

So this could have been a rather mellow occasion. We had started the organisation as a defiant response to what came to be known as ‘Section 28’: a small measure that was part of a sprawling local government bill and intended to stop the ‘promotion’ of homosexuality in schools and by local authorities. In trying to mobilise opposition to the measure we’d been encouraged by the sense of purpose we’d found — and by a good deal of public sympathy and support. So we had determined not to let the momentum be lost.

That was 25 years ago and it’s fair to say our cause had succeeded beyond our wildest early hopes. An anniversary dinner could have been the occasion for celebration, reflection, some mutual backslapping and a little dash of discreet self-regard. That’s what anniversary dinners are for; and that’s the impression conveyed skilfully by the video: cordial, uplifting and faintly worthy.

But, oh my goodness, that isn’t the dinner I recall. The whole thing bristled with submerged hostilities. I won’t bore you with them, they’re too tedious for words, they don’t matter, and anyway I played some part in stirring them. Suffice it to say that when I accused a colleague I actually like and admire of gassing on for too long, there was a small explosion. We both calmed down and climbed down but the incident (beautifully excised from the video) was indicative of other tensions — not all of which I understood at the time — beneath the surface. Some of us were reeling by the time we left; and life is too short to analyse why.

But not too short for a wider question. What is it about voluntarism, what is it about organisations composed of public-spirited people giving of their own time and money for some purpose larger and nobler than themselves, that breeds the poisonous atmosphere that so often chokes their deliberations? Why do volunteers become so nasty to each other?

I’ve spend what seems a lifetime negotiating these perilous waters. Voluntary Conservative politics has been my nursery, and a more sulphurous, spitting, clawing, feuding and backbiting introduction to the spirit of voluntarism you couldn’t hope to find. Except you could. I’m told Labour activism is even worse. Liberal Democrats do little but gossip maliciously about each other. And Ukip’s local organisations are said to be at all times no more than one gunshot away from a civil war.

Nor is the problem peculiar to politics. Ask any charitable group. ‘Internecine’ doesn’t do justice to the undercurrents of resentment. It’s commonplace, come the annual general meeting, for nobody to want their name to go forward when nominations for (say) hon. secretary are sought, for somebody finally to be persuaded to concede that, well, OK, if nobody else will do it, he or she will — and then for members to spend the rest of the year complaining about the way this volunteer does the job. The levels of resentment against other persons, and the levels of righteous fury in disputes about policy and purpose, are phenomenal. Thus people working for a wage in a bomb factory are likely to be far less aggressive than people working for nothing in a disarmament charity.

Why? Here are three possible candidates for an explanation. The first is that cantankerous and self-righteous individuals are disproportionately attracted to voluntary societies. According to this theory, people actually join in order to find themselves an arena in which to be disputatious. We can all think of friends who qualify for this description, but I cannot believe it’s the only explanation. We can equally all think of friends who are sweetness and light in every sphere of their lives except volunteering — when something dreadful seems to come over them, and a committee room becomes a snake-pit just when calm is needed.

The second theory, not unrelated, is one of which C. Northcote Parkinson would have approved, and is an example of the old saw about disputes between academics: vicious because the stakes are so small. To vary Parkinson’s Law, spite expands to fill the time available. Many who join voluntary organisations have time on their hands and nothing else to do. The Devil then makes work to fill the lacunae: they squabble and intrigue about nothing as a kind of recreation, but one with the added advantage of being (so they tell themselves) public-spirited. There’s plainly some truth in this theory but, again, it cannot explain the vitriol that can infuse a voluntary body even when its work is urgent and demanding, everyone’s very busy, and cooperation is critical to its success.

It’s to my third possible explanation that I particularly draw your attention because I think it has been overlooked: that when we are ‘giving up our own free time’ for no advantage to ourselves, we become very difficult to command. The disciplines of a management structure, concepts of professionalism, the unifying simplicity of the pursuit of profit, all lose their purchase when we are not being paid to work. We are working for our beliefs — our beliefs, not somebody else’s. Thus we are released from the usual rules of the workplace.

Samuel Johnson never spoke truer than when he said that a man is never more innocently employed than in the pursuit of money. The pursuit of principle is an infinitely more corrupting thing.