Jemima Lewis: It is a relief to hear Cameron the curmudgeon

The values rap promotes are unintellectual: all drooling materialism and brute force

The Conservative leader this week became the latest in a long and beleaguered line of politicians to draw a link between gangsta rap and rising violence. In particular, he criticised the Radio 1 hip-hop DJ Tim Westwood for playing music that "encourages people to carry guns and knives". No sooner had the words left his mouth than he seemed to curl up into a defensive ball: he would, he gloomily acknowledged, "get a lot of bricks thrown at [him]".

Sure enough, the kids are outraged. "Why are they hating hip-hop and rap for," writes one contributor to Radio 1's chatroom debate. "These old maz dont know shizzle and go on like these youngsters today listen to too much hip hop and rap which mess's the minds and makes them carry knifes and guns. its not that at all its peaple doing what they do and get beef with other manz then need something for protection."

The BBC's official response was more easily deciphered, but hardly less enervating: "Hip-hop is a huge international genre with a vibrant UK scene, and that music reflects the sometimes harsher realities of people's lives and cultures."

This is the argument that liberals have been trotting out for two decades: rap is just a reflection of life in the ghetto, and if we don't like it we should address the social problems behind it rather than the music itself. Besides, they add, why pick on black culture? Death metal groups cultivate a bloodthirsty image, and nobody picks on them.

This is not entirely true - witness the scapegoating of Marilyn Manson after the Columbine massacre - but it contains a seed of truth. People do worry about hip-hop much more than death metal, and for good reason: the former is the most popular genre of pop music in the world, while the latter is beloved only of engineering students, unpopular schoolboys and Finnish Eurovision entrants.

Hip-hop has become much more than just a type of music: it is the driving force behind contemporary youth culture. Look at any teenage boy - the slouching gait, the prison-white trainers, the perilously low-slung trousers (a homage to American convicts, who are not allowed to hold up their standard-issue trousers with a belt) - and you see the vice-like grip of rap culture upon the juvenile psyche. But fashion influences are much easier to prove than behavioural ones. There are so many variables: class, genes, family background, education. It goes without saying that the mere act of listening to a rap song won't turn an innocent schoolchild into a Glock-wielding maniac. Of this I am living proof.

In 1988 - the year that gangsta rap entered the mainstream with Straight Outta Compton, by Niggaz with Attitude - I was studying for my A-levels at a posh London girls' school. Like the rest of my classmates, I went to great lengths to appear "street": I listened to hip-hop, smoked weed and wore baggy tracksuits with old-school Nike high tops.

None of us was remotely outta Compton: we lived in book-lined houses in Barnes or Notting Hill, with parents who were publishers, architects and journalists. Yet we listened to songs such as "Fuck Tha Police" and nodded knowingly, as if they spoke for us.

Privately, I was always alarmed by lyrics such as: "A young nigga on a warpath/ And when I'm finished, it's gonna be a bloodbath/ Of cops, dyin' in LA." A law-abiding creature to my fingertips, I had never so much as shoplifted, let alone disrespected a policeman. I found the use of the N-word distressing, and I didn't at all approve of women being referred to as "bitches".

On the other hand, there was an authenticity to that early gangsta rap that defied censure. The fury and alienation behind it - hitherto barely expressed - were awesome to behold.

The problem is what happened next. The gangsta rappers became rich and famous (those who weren't gunned down first), and bling replaced rage. Contemporary rappers such as 50 Cent parade their ghetto backgrounds not as evidence of social inequality, but as a mark of machismo: a passport to riches, women and respect. Swathed in diamonds and dollybirds, they swagger about like self-satisfied plutocrats, not victims of circumstance.

Which brings me back to their apologists. The best way to address violence and criminality is, of course, through education - but gangsta rap makes it harder to do that. The values it promotes are profoundly unintellectual: all drooling materialism and brute force. In a peer group that derides learning, many talented children will be too frightened to fulfil their potential.

There's no need to ban gangsta rap, but neither should we turn a blind eye to its failings. As NWA's Ice Cube put it: "Do I look like a mutha fuckin role model? To a kid lookin' up ta me/Life ain't nothin but bitches and money."