Were it the case that the proposed mandatory addition of folic acid to bread was intended solely to benefit the health of the person eating it, then I might have some sympathy, on grounds of freedom of choice, with those who object to such compulsion.
However, it is morally wrong to knowingly withhold such a measure when it is intended to enhance the health and well-being of the unborn infant; a low folate level in a pregnant woman will greatly increase the odds that her baby will be born with spina bifi da: the evidence from international research is freely available and rock-solid. Now, by definition, a foetus cannot express its preference (even if it were aware of any), and so it falls to a responsible adult to decide on its behalf - in this case, by taking folic acid supplements.

We nominally deem the expectant mother to be this person - but, regrettably, not all such women act responsibly, either through ignorance or laziness, or just
occasionally, contrariness. Therefore it falls to society to step in, because a foetus is more than a mere chattel to be treated according to the whim of its bearer: if there is a known risk and, equally, a known protection against that risk, then it is ethically imperative, on grounds of both assumed autonomy and utilitarianism, to act.
The claimed hazards of folic acid, when consumed as an additive in bread, are minimal; certainly, they pale into insignificance when compared with those of our favourite intoxicant, ethanol, even when this is drunk in modest quantity.

Finally, baker Nick Parker has neatly shot himself in the foot. His excellent bread may well contain plenty of folate, but if, as he claims, the commercial stuff is short of it - and it's mass-produced bread that most people buy - then the addition of folic acid becomes necessary.
Artisans such as he could apply for exemption, provided that they could demonstrate an adequate folate level in their own product, which people would be free to buy instead - and then we would all be happy.

Graham Cliff, Katikati.