Howard Jacobson: If what we watch or read can move us to compassion, it can move us to sadism too

There is an unwillingness to believe that our times are morally or intellectually inferior to any other

I have always had a soft spot, against my own interests and predilections, for the censorious of mind – Jeremiah, Jonathan Edwards, Malvolio, Mrs Mary Whitehouse. I fought my English teacher at school about Malvolio. He accepted at face value the view of him expressed by Sir Toby Belch and the other carousers and tormentors in Twelfth Night – as a killjoy who thought because he was virtuous there should be no more cakes and ale, yet fell at the first temptation to pleasure that came his way.

To me Malvolio was a hero of seriousness, in the face of whose scorn the hedonism of a bunch of soaks showed its true complexion of idle malice. That he could turn in a trice from puritan to lover was not, to me, a mark against him. Of course the passionate will love as fervently as they hate. The dialectic of the heart and all that. For which reason it is wrong to suppose that what makes them human makes them, as scourges of humanity, hypocritical. All the best flayers of weakness and indulgence know what weakness and indulgence feel like from the inside.

Mrs Whitehouse was silly half the time, passing off mere prudery as morality. But that made her telly's perfect adversary, since half the time its much-vaunted boldness was nothing more than prudery inverted. That was how BBC2 chose to tell the story last week in Filth: the Mrs Whitehouse Story – as a battle between a naive if determined woman who saw naughtiness everywhere and a director-general of the BBC who was pretty much the same, only she didn't like what she saw and he did. A merry romp was therefore what we got, but little to make us think about the rights of free expression, the place of censorship, and the vexed question of if and how the things we watch affect the things we do.

Newsnight mounted a brief discussion after the play, too brief to push the arguments much further. But Roy Hattersley, confessing he had not agreed with Mrs Whitehouse at the time but had no difficulty agreeing with her now – and he is not, I suspect, alone in that – hit upon the right word when he said that, whatever else, television had "familiarised" us with violence. What the consequence of that familiarising is, is anybody's guess. No test will ever establish a direct link between an image seen, an emotion provoked, and an action performed. So, no, you can't with certainty attribute contemporary knife-wielding among the underaged to the violence they've seen on films, television, or whatever virtual-reality murder toys they play with. But you can't with certainty deny the association either.

What astonishes me is that anybody would want to. Since we know that what we watch and read is capable of moving us to tears of compassion, and not necessarily passive, soon-to-be-forgotten compassion, as witness the charitable giving television is able to inspire, it stands to reason that it can variously move us to rage, to pain, to jealousy, to lust, and not necessarily soon-to-be-forgotten sadism, too.

Says the liberal intellectual, "But there has always been violence in literature. Think of Hamlet stabbing Polonius behind the arras." As though art is not self-selecting. As though "How now? A rat? Dead for a ducat, dead!" will pass from Hamlet's lips to those of the wordless thugs sitting in the grand circle of the Royal Shakespeare Theatre sharpening their rapiers.

There is an unwillingness among secular liberal intellectuals to accept the idea of a fall, to believe that our times are morally or intellectually inferior to any other, or that there are some within our society who to all intents and purpose have fallen out of it. Ideologically, relativism is in the wind. Amy Winehouse is the equal of any Elizabethan lyric poet, and today's gang culture is no different from any other's.

We are hypocritical in this: populist on principle, elitist in practice. We spend more in a restaurant in a night than the average 14-year-old old knife-wielder's family earns in a week, take pains to dwell in utter ignorance of how life is lived, let alone taken, outside Islington or Hampstead, but affect a conviction of democratic sameness, so that if a bit of violence on telly doesn't bring us out rampaging on to Haverstock Hill we cannot imagine why it should have that effect on someone living unemployed and angry in a sink estate in Dewsbury.

Thus: nothing has changed, our cities have always been violent, television cannot possibly be at fault, and if you must blame anybody (for what isn't actually happening), then blame the parents. Which raises, does it not, the question of who or what made the parents.

And which leaves me missing Mrs Whitehouse. I am half-inclined to say I wished she had been less fastidious in matters of sex and concentrated her zeal more on matters of brutality. She was not subtle enough, morally or aesthetically, to understand the difference between an exhortation to lust and the depiction, as often as not lamentable – at least in the hands of a serious writer – of lust's progress. But I no sooner make that distinction than I hear its sophistry.

If we are to argue that television and the trash subculture of magazines and papers which it has spawned contribute to the national tone, and in that way to the emotional education or otherwise of those who carry knives, and before that to the parents of those who carry knives, then we cannot neatly separate sex from violence, or sex and violence from celebrity, or celebrity from fame and greed, or fame and greed from triviality, or triviality from worthlessness, or any of the aforementioned from the all-round cheapening of life which was ultimately the target of Mrs Whitehouse's Christian campaign.

We have trouble with the Christian part if we are liberal humanists. But again we make the mistake of assuming that if humanism has worked for us, out there where it's safe, it should work just as well out there where it isn't. We forget the religious bedrock of decorum and decency on which our humanism is built. Some of my best friends are humanists, but there's not a one on whom you can't smell the long-anterior influence of the ethics which religion once taught.

And where they never were, or have been long forgotten, and where that day-by-day seepage of lowering does its demoralising work – what then? Knives, reader, might just be the start of it. And we'll look back to Mrs Whitehouse as to a golden age.