Amy Jenkins: This fantasy of niceness denies us healthy anger

As Jung and Freud knew, dark feelings should be invited out into the light

Tread on a worm and it will turn, so the saying goes. And Nick Clegg's worm certainly turned on Thursday night.

In fact, it reared up and bit off two rather famous heads: the "worm" in this case being a worm poll or "dial test" conducted among focus groups who watched the leaders' debate and responded in real time by turning a dial of approval up or down. Invented in America, the worm poll creates a graph line that wriggles across the screen as the punters respond.

Interestingly, one of Clegg's biggest peaks was when he said of Brown and Cameron: "The more they attack each other, the more they sound the same." So why did this get such a big response? No doubt we're all jaded by the same old right-left argy-bargy, but beyond that I suspect "attack" was the operative word here. It is well known that voters dislike Punch and Judy politics. It seems people want their politicians nice.

Not me. As far as I'm concerned, the word "nice" conjures up terrible visions – a sort of John Lewis land of polite society, of "ladies" and orderly queues and people who say "passed on" instead of dead. Why don't I like it? Because underneath an imposed culture of niceness, there'll be seething resentment about all the things that haven't been said. Niceness is the big British cover-up. Nothing is as toxic.

Now, don't get me wrong – there's nothing wrong with being kind. I'm all for kind. The point is that positive emotions need to be genuine – unless it's a form-filler like saying thank you (note that negative emotions are rarely faked, not being mandatory.) Politeness has its place – but mostly in formal situations and where strangers are concerned. In more intimate situations it can be a killer. One therapist I know says he regularly sees couples who are on the point of divorce because one hasn't got the guts to tell the other that their breath smells.

It is really simulated niceness that I can't stand. It is when someone rings up from a call centre and says, "How are you?" Generally I try to behave decently with people in call centres – they are only making the best of a bad business – but when they start with "How are you?", I immediately want to slam the receiver down. It's the phoniness of it – no pun intended.

In The Catcher In The Rye, Salinger's anti-hero Holden Caulfield sums up teenage rebellion for ever with that one word: phony. As far as he's concerned, adults are all phony. This is the teenage rite of passage to conformity. A teenager will always be angry about all the ways he has to squash himself to be acceptable to society – to be "nice". So it's not just politicians who must continue with the Punch and Judy – we all need to be encouraged to have healthy conflict. Otherwise the negativity (and there is always going to be negativity) goes under the surface where it is dangerous. Ask Jung. Ask Freud. These dark feelings should be invited out into the light.

One of the reasons why I loved the US sitcom Friends was because of the robust way the characters dealt with conflict. It was very un-British. They regularly aired their irritations with each other in a way that wasn't loaded with a darker shame (the shame of not being "nice"). Monica and Rachel, with the aid of a savvy bunch of New York scriptwriters, regularly dressed down each other's characters with brutal precision. They definitely weren't nice to each other in these moments and yet this was portrayed as a pretty good and healthy way to conduct a friendship. There was a forthright flavour to the conflict that was exhilarating.

My two best friends are a couple and they're one of the most loving couples I know. We often sit over dinner and they tell me how much they annoy each other. There's some real feeling in the account – some real pain – but there's also a lot of laughter and honesty in the mix. These two don't do the social niceties and it makes them tough to be friends with sometimes – but also the best, most refreshing people you can imagine. If one of them drinks too much, the other says: "Stop that at once. You're slurring your words. It's embarrassing." They don't care who's listening. It may not be nice, but it's honest and there's nothing worse lurking underneath the actual words that are being said. The told-off one takes it on the chin – it goes the other way just as often. Then they go home happy – no toxic silences in the car about things that haven't been said.

So let's ditch this fantasy of niceness. It denies healthy anger, it doesn't suit honesty and, in the end, it doesn't lead to happiness either. As for politics, we need our politicians on the attack. We need them angry if we want them passionate. We need them to be lions, not nice little mice.