Joan Smith: Rage is the product of a coarser age

There are some crimes so abhorrent that they make us wonder what kind of society we're living in. One of these bouts of soul-searching was prompted last week when a man died after a violent altercation in a Sainsbury's supermarket in south London; a man and a woman have since been charged with the murder of Kevin Tripp, a 57-year-old engineer from Colliers Wood.

Shocked friends and neighbours paid tribute to Mr Tripp, who suffered from ME, and there were harrowing pictures of the grief-stricken mother of his five-year-old daughter. Several lives have been destroyed by an event that was over in seconds; and another child – like those of 47-year-old Garry Newlove, who was kicked to death in Warrington last August – now has to grow up without a father.

Mr Newlove was set upon when he challenged a group of youths who were damaging a car. Mr Tripp was attacked, apparently after a row over queue-jumping. What was especially shocking about these deaths is that none of us expects to encounter lethal violence in everyday life; we don't kiss friends and partners as they set off for Sainsbury's, crossing our fingers and desperately hoping they'll survive the trip. Crime surveys tell us that such extreme events are relatively rare, but the phenomenon they appear to highlight – an increase in aggressive behaviour – is causing great concern.

Evidence is accumulating that substantial numbers of people have never learned to handle anger and aggression, reacting with uncontrolled fury to minor setbacks and slights. Alcohol sometimes plays a part, but random flare-ups of hostile behaviour have become so common that we talk about road rage, air rage, even supermarket rage, as if they're a normal part of existence. Drive slowly when you're lost, and you may see the faces of other drivers contort with anger as they try to overtake. Politely ask the person in front of you on a plane not to slam their seat back, and they're likely to let loose a stream of abuse. Adults' behaviour affects children, and bullying is now a major problem in schools, where kids use text messages and the internet to persecute vulnerable classmates.

None of this is happening in a vacuum, and it's perverse to deny a link with popular culture. Everywhere I look, aggressive behaviour is egged on and validated, whether it takes the form of celebrities being encouraged to slag each other off or TV chefs haranguing their hapless assistants. Big Brother and its spin-offs choose contestants with poor impulse control and an infantile desire for attention, cynically pitting them against each other.

Nowhere is this more evident than on the internet. Many people who post messages seem to be in the grip of ungovernable rage, which they direct randomly at anyone who comes into their sights, like drunks lurching out of a pub in search of a punch-up.

The urge to insult, hurt and humiliate is clearly part of human nature. But it is more prevalent in some cultures than others, and its antidote is just as well-known. Civilised societies don't reward displays of petulance and anger. They certainly don't pretend that good manners are only for wimps.