The surprising thing about the reaction to the appalling behaviour reported from The Presidents Club fundraiser is that people are so surprised by it.

The reaction to the revelation by undercover journalists that rich men groped and harrassed pretty young female hostesses reflects the public triumph of a certain liberal narrative: that we're basically good people, that the world is getting better and that we are learning to behave ourselves thanks to hashtags and the Twitter-shaming of people who step out of line. 

Unsurprising, however, is the number of men who were there, but claim to have 'left early'. Among them were children and families minister Nadhim Zahawi, who claims he didn't see anything, and David Walliams, the host. Perhaps they didn't, but it would be interesting to know how many of those who were there told their wives they too had left early.

I'm as revolted as anyone by the thought of so many rich men abusing women 'bought as bait', in Labour MP Jess Phillips' resounding phrase. But surprised? No.

Get enough people together in a place where social norms are suspended and they have permission to behave badly, and the chances are that they will. Think Abu Ghraib during the Iraq war, where generally decent people committed atrocities because they could. Add alcohol, which removes inhibitions, and it's a virtual certainty; think a Blackpool hen night. Our codes of conduct and public conventions are, as CP Snow put it, just a coat of varnish. Underneath, all the old instincts are alive and well.

The idea that we can declare particular language or behaviour unacceptable and somehow change people only works up to a point. It shames people into public compliance, and it might make life a bit easier for people – usually women – who would otherwise be forced to accept Presidents Club stuff as normal. Good: but let's not pretend anything has really, at a fundamental level, changed in human hearts. If we believe that, we'll be led into a fatal complacency.

When attitudes and opinions can't be expressed in public, they'll go underground. The liberal niceness project will be increasingly hollowed out, with a veneer of civilised discourse disguising the resentment and contempt of those who feel they aren't being heard. (This, among other things, is one of the drivers of the extraordinary reaction to Cathy Newman's drubbing at the hands of Jordan Peterson in the now-famous Channel 4 interview: a series of slogans disguised as questions were exposed as groundless posturing.)

Does this mean we shouldn't try to improve standards of public behaviour? Of course not. Nothing like the Presidents Club debacle should be allowed to happen. But it will, of course, and no amount of finger-wagging will stop it.

The Christian take on this is rather different. We are, if we have read our Bibles, more clear-eyed about human nature. We believe in original sin, and that the heart of man – usually men, though not invariably – as well as having extraordinary traces of residual goodness, is deceitful above all things and desperately wicked. Change begins when we acknowledge the strength of our instinct for doing wrong. It isn't as simple as complying with an edict from a company HR department.

One of the seminal novels of the 20^th century was William Golding's Lord of the Flies. It portrays the breakdown of civilisation among a group of British schoolboys stranded on a desert island during the war, their descent into tribalism and savagery. In its most disturbing scene, a chaotic, primitive feast results in the frenzied killing of one of the boys as their primal instincts are unleashed. Afterwards, there's a corporate denial of what they've seen and done:

'Memory of the dance that none of them had attended shook all four boys convulsively.

'"We left early."'

It's a profoundly disturbing novel, because it's true: take away the structures that govern how we interact and what we believe about right and wrong, leave us to our own devices, and see just how much of our vaunted civilisation is left.

We can achieve a fair bit by changing the public discourse. But to change a human heart requires a far deeper transformation. That's where the gospel comes in – another disturbing idea for a society that has decided it has no need of God. And in the light of the gospel, 'We left early' doesn't cut it: we're all responsible for what we do.

Follow Mark Woods on Twitter: @RevMarkWoods