In a dramatic public letter to all National Childbirth Trust (NCT) stakeholders – it finishes, “please keep on keeping on, if you can” – its president Seána Talbot has resigned. There is clearly a lot of personal chagrin (Talbot talks of coercion, bullying, a toxic culture, mistrust between staff and volunteers) which would be unfair to adjudicate from a distance. She laments the organisation losing members – a drop of 55% since 2016 – although doesn’t mention that since 2015 it has not been obligatory to become a member in order to take the prenatal classes.

However, competitors have sprung up in the prenatal business, organisations parents-to-be prefer because they’re less expensive and less doctrinaire: in many ways, the surprising thing is that the NCT dominance lasted so long, given that for years the trust has been known for its fierce views on the “medicalisation” of childbirth. Women came away with the idea that epidurals were for wimps, caesarean sections meant you had failed, and the Syntocinon injection was only for the kind of weakling who couldn’t eject a placenta with the power of her mind. To be fair, 60 years ago, this started as the “natural” not “national” childbirth trust.

The kernel of the dispute, as Talbot sees it, is this: “The executive team has taken the charity away from our core mission of birth and breastfeeding, and towards a more generic ‘parent support’ with an emphasis on postnatal mental health.” The charity doesn’t dispute that postnatal depression is, currently, where most of its resources are going (via a campaign called #hiddenhalf), but contends that this and breastfeeding support are not mutually exclusive.

In fact, though, they are: when your position is that breastfeeding is the only real choice of the responsible mother, it’s difficult to claim a meaningful, simultaneous care for her mental health, and often this orthodoxy works actively against her confidence and mental wellbeing.

Feeding is the ultimate parenting culture war. The principles are absolute (breastfeeding is only good, bottle-feeding only harmful); the borders policed (breast milk, exclusively, for six months, which is vanishingly rare in real life). This ideal was evangelised until it became a public health standard that very few women could meet. Crucially, breastfeeding advocates react very badly to any notion of coexistence – that mothers who bottle-feed can enter the same conversations, forums, Instagram feeds, on the same terms. They will always be suboptimal mothers, though it won’t be their fault – rather, they didn’t get enough “support” to do the right thing.

The trajectory of this has been interesting; it started with a battle against priggery, that women should be able to breastfeed in public. Twenty years ago, I wrote my first column for these pages; a rant against that campaign. I didn’t mind the feeding. But in a bid to normalise it in public places, someone had railed against the “sexualisation” of breasts, which seemed to distil something of the self-righteousness of parenting: we all had to have our breasts culturally desexualised, just because some of us might need them, for a time-limited period, for something else.

In retrospect, I can see the virtue of that drive – rates of breastfeeding climbed, steadily from 2000 to 2010, according to the Infant Feeding Survey carried out twice a decade since 1975 (then discontinued by the coalition government as part of its general corrosion of the fabric of society). Still, it was unfortunate that the point had to be made by dividing women – in this case, into mothers, who were using their breasts properly, and non-mothers, who weren’t.

Yet a more damaging division was sown by the growing certainty of the pro-breastfeeding position: its health benefits were ever more trenchantly stated. It didn’t just protect against a tummy bug; it protected against cancer. It wasn’t just a tender, beautiful connection with your baby; you couldn’t bond properly without it.

The methodology was often problematic – unless you could point to a specific mechanism, some element of breast milk that could account for the higher IQ, or the superior digestive tract, you would always return to this impossible conundrum. How do you distinguish, causally, between the benefits of breastfeeding and the benefits of being the kind of mother – vigilant, informed, obedient – who decides to breastfeed? Had this been a neutral medical space, like a fungal nail infection, a compromise position would have been reached; this seems to work, but if it doesn’t work for you, try something else. But the space was anything but neutral: breastfeeding got into a feedback loop with a distinctively 21st-century risk aversion around every element of mothering, from a woman’s behaviour in pregnancy to her single-mindedness as a caregiver.

It was, in my view, part of a wider drive to situate every conceivable problem a person might have, from obesity to poor housing to being bad at maths, as their own individual failure, or if that wouldn’t fly, the failure of their mother – a necessary ideological precondition to unpicking our collective insurance structures against misfortune, known broadly as “the welfare state”. But – like the benefits of breastfeeding, in fact – that’s quite hard to prove, so it’s not a hill I’d die on. The upshot has demonstrably been a rigidity that leaves huge swathes of women – for reasons practical, economic, physical, medical, personal – feeling judged and unworthy, and codifies women by class, at a time in life when social distinction seems least relevant and most absurd.

I would like to see a new wave of parenting campaign energy, its founding principles: “Is anyone hungry? Is everyone happy?” This is what the NCT is already doing, in directing itself towards mental health, and in the process towards a more inclusive attitude to infant feeding. But the spirit of compromise, of good enough, of whatever works, is itself deeply political, an existential challenge to the creed of parental perfection, and this internal strife at the NCT is just the beginning.

• Zoe Williams is a Guardian columnist