Natural Law is the inbuilt, universal human understanding of the good - the true, beautiful and virtuous.
Modern people violate this, the modern state propagandises the violation of Natural Law, the violation of Natural Law is taught explicitly, and inculcated covertly, by the 'arts' and entertainment and news.
(I mean that personal experience and observation are meaningless or intrinsically mistaken, that lies are truth, and truth is hate; that beauty is kitsch and deliberately-contrived-ugliness is true beauty, and the reversed/ inverted sexual morality which forms the focus of so much modern public and personal life where what was bad becomes a subsidised and coerced good, while what was good is labelled an agent of cruelty.)
It is not because of stupidity. Everybody already knows (by its definition) Natural Law. But under Leftism people know it only to violate it. And this is evil - intentional, purposive, deliberate evil.
To put it another way, the main problem is that people are not even not-even-trying to be good; they are actually trying to be bad, because they believe (because they are told, 24/7, and punished if they disagree) that bad is good.
(But 'people' are not innocent victims of this evil propaganda - they contribute to it and profit by it and try to exploit it for their own ends; they are culpable, they are blame-worthy - they will be held to account not for that which was coerced upon them, but for their self-interested propagation of the ideology which rationalizes this coercion.)
This is why there is no atheist solution to the current problems, it is why the secular Right is of no use; and why paganism is no use - why (ultimately) only traditional devout monotheism can and will defeat Leftism.
Nothing else than monotheism has the solid transcendental core to withstand the multifaceted worldly materialism of Leftism.
In the past, before the triumph of the Left, human society would 'naturally' be regulated by Natural Law.
But we are now in a situation in which Natural Law is regarded as evil.
(Evil because a universal tyrant, an inescapable and exclusive code of behaviour, a strangling constraint on freedom of self-development; because NL makes some people suffer - suffer either absolutely, or relatively compared with what they ideally-might experience... and so on.)
Therefore reminding people of universal values is worthless, or even harmful - because modern Leftism is precisely about violating and inverting Natural Law ('subverting' is their favourite term).
Argument is useless - the Left knows the arguments anyway (since they are common sense and based on universal knowledge and experience); but they will not argue.
The Left know that their own arguments are incoherent but have chosen to embrace incoherence as a sign of their own depth of moral conviction.
In fact incoherence is a sign of enthrallment to purposive evil, reflecting that evil is incoherent (because negative, destructive by its nature - the anti-Good does not need to be coherent).