Like most of Chesterton, this is theological polemic. But it is good theological polemic. His use of the Manichee as an example of liberal hypocrisy (he was writing a century ago) works because the Manichees were gnostics, and like the modern gnostic prattling about spirituality or mindfulness, the perfect follower of Manichee limited his life for religion.

To set the light-substance free from the pollution of matter was the ultimate aim of all Manichæan life. Those who entirely devoted themselves to this work were the “Elect” or the “Perfect”, the Primates Manichaeorum; those who through human frailty felt unable to abstain from all earthly joys, though they accepted Manichæan tenets, were “the Hearers”, auditores, or catechumens. The former bear a striking similarity to Buddhist monks, only with this difference that they were always itinerant, being forbidden to settle anywhere permanently. The life of these ascetics was a hard one. They were forbidden to have property, to eat meat or drink wine, to gratify any sexual desire, to engage in any servile occupation, commerce or trade, to possess house or home, to practice magic, or to practice any other religion. Their duties were summed up in the three signacula, i.e. seals or closures, that of the mouth, of the hands, and of the breast (oris, manuum, sinus). The first forbade all evil words and all evil food. Animal food roused the demon of Darkness within man, hence only vegetables were allowed to the perfect. Amongst vegetables, some, as melons and fruit containing oil were specially recommended, as they were thought to contain many light particles, and by being consumed by the perfect those light particles were set free. The second forbade all actions detrimental to the light-substance, slaying of animals, plucking of fruit, etc. The third forbade all evil thoughts, whether against the Manichæan faith or against purity. St. Augustine (especially “De Moribus Manich.”) strongly inveighs against the Manichæan’s repudiation of marriage. They regarded it as an evil in itself because the propagation of the human race meant the continual imprisonment of the light-substance in matter and a retarding of the blissful consummation of all things; maternity was a calamity and a sin and Manichæans delighted to tell of the seduction of Adam by Eve and her final punishment in eternal damnation. In consequence there was a danger that the act of generation, rather than the act of unchastity was abhorred, and that his was a real danger Augustine’s writings testify.

This basic hatred of the body ends up with a hatred of the creator. And this, Chesterton, skewers.

The Modern Manichee.

He sayeth there is no sin, and all his sin
Swells round him into a world made merciless;
The midnight of his universe of shame
Is the vast shadow of his shamelessness.
He blames all that begat him, gods or brutes,
And sires not sons he chides as with a rod.
The sins of the children visited on the fathers
Through all generations, back to a jealous God.

The fields that heal the humble, the happy forests
That sing to men confessed and men consoled,
To him are jungles only, greedy and groping,
Heartlessly new, unvenerably old.
Beyond the pride of his own cold compassion
Is only cruelty and imputed pain:
Matched with that mood, a boy’s sport in the forest
Makes comrades of the slayer and the slain.

The innocent lust of the unfallen creatures
Moves him to hidden horror but no mirth;
Misplaced morality rots in the roots unconscious,
His stifled conscience stinks through the green earth.
The green things thrust like horrible huge snails,
Horns green and gross, each lifting a leering eye
He scarce can call a flower; it lolls obscene,
Its organs gaping to the sneering sky.

Dark with that dusk the old red god of gardens
Still pagan but not merry any more,
Stirs up the dull adulteries of the dust,
Blind, frustrate, hopeless, hollow at the core;
The plants are brutes tied with green rope and roaring
Their terrible dark loves from tree to tree:
He shrinks as from a shaft, if by him singing,
A gilded pimp and pandar, goes the bee.

He sayeth, ‘I have no sin; I cast the stone’,
And throws his little pebble at the shrine,
Casts sin and stone away against the house
Whose health has turned earth’s waters into wine.
The venom of that repudiated guilt
Poisons the sea and every natural flood
As once a wavering tyrant washed his hands,
And touching, turned the water black with blood.

Gilbert Keith Chesterton

In our fallen time it is not stones they cast at Christ, but regulations of what is appropriate speech. Which turns water not into wine, or blood, but sepsis.