One of the most depressing things about politics in the UK is realising how easy it is for total nonsense to become common sense and received wisdom.

Take this tweet from YouGov, following the recently announced rise in fares. “There will be calls for train fares to be frozen – the main beneficiaries will be those in wealthier households. 42% of those who made more than 50 train journeys last year are in households earning £40k+. Just 10% are in households on less than £20k”. Most of the poor, YouGov sagely intones, take the car, or bus, or walk. Therefore we should not lower the price because that means only rich people will benefit.

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It doesn’t take a genius to work out that “people with more money use expensive services more than people with less money” isn’t that shocking a finding. However, our collective discussion of class and wealth is so muddled that we often find this kind of argument being rehashed without a second thought. The poor use cars more, presumably, because their honest, working-class culture makes them more likely to – rather than, say, because they live in areas that are poorly served by public transport, or that the trains are hideously expensive. We assume that usage patterns are locked in, and will remain unchanged if price and availability changes.

The same basic mistake gets reheated over and over whenever anyone suggests anything even approximating a universal provision of services. Kate Osamor shouldn’t get a council house because they should be reserved for the poorest. Child benefit is unfair because a very rich person will get it, too. Tertiary education is mostly consumed by the middle class and therefore making it cheaper will only benefit those who currently benefit. Only wealthy people can now afford to live in city centres, and therefore increasing housing stock in these locations will benefit only the wealthy.

The biggest problem with this argument is that if you think about it for only 30 seconds it seems fairly sensible. Of course in a system with limited resources we should prioritise access to those resources for those who need them the most. However, people are falling for what Chris Dillow calls the Fairness Error – “expecting each individual transaction to be egalitarian and are overlooking the costs of doing so”. We would not expect a pub landlord to charge people different prices based on income, with a pint of beer costing some 20p and others £20. Even if such a system might be theoretically perfectly fair, we would recognise the almighty mess it would cause in practice. What matters is that the overall system is fair, on balance, not every individual action.

YouGov (@YouGov) There will be calls for train fares to be frozen - the main beneficiaries will be those in wealthier households. 42% of those who made more than 50 train journeys last year are in households earning £40k+. Just 10% are in households on less than £20k https://t.co/FjIiaeD86d pic.twitter.com/mRznAzMnRW

Ironically, although they may not be aware of it, by engaging in this egalitarianism of fools, those who decry universal solutions are obstructing access for those most in need.

Means tests create a fertile ground for the politics of middle-class resentment. Those just over the boundaries of means testing often feel as if they are unfairly paying over the odds to prop up those only a little behind them. This decreases political support for services, and increases support for more onerous and punitive means testing to ensure only the most “deserving” get any help at all. This increase in bureaucratic burden swallows up any efficiency gains we may get from better targeting, and often counterintuitively means that the most vulnerable are even more locked out by the wall of paperwork and eligibility testing.

Would making trains cheaper benefit the wealthy? Yes – but before the NHS or comprehensive free education you could have made exactly the same argument about them. These things are unmitigated goods for everyone in our society, and disposing of them now because “the middle class can afford to pay their own way” would be recognised as absurd.

Those who struggle to see why making things cheap or free benefits everybody tend to be stuck in a way of thinking which should have been long discarded. They believe that things are basically OK and that the system only needs a few tweaks – generally because they are in the shrinking demographic for which things are, indeed, basically OK.

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Increasingly, though, we are looking at this from outside that privileged vantage point. The crumbling foundations of late capitalism are making more and more people aware that the entire system is unsustainable, and that is even before we look at the onrushing tsunami of climate change which will require vast and radical change within a couple of decades or less. We are no longer interested in simply tinkering – the whole thing needs an overhaul. As a result, we cannot evaluate policies through a “let’s assume everything else stays unchanged” frame. Assume everything has to change, because it does. What do we want to change it to? And how can we best do that?

Let’s unmuddle our thinking on these issues. If we want to ensure fairness, we should not simply try to target services and goods used by the very poorest but ensure equality of access for all. If that feels too unfair because the rich benefit too, then there is a fair and simple solution: tax the rich.

• Phil McDuff writes on economics and social policy