A new game for summer, rich in opportunities for gratuitous insult - Schweizerize your friends! Play it amid High Tory grandees at Glyndebourne, or down at the Winnie Mandela House gay'n'lesbian playscheme. All you need is a book (or a handy digest, which I will try to provide) written by a research Fellow at the Hoover Institution at Stanford University, Peter Schweizer.

He has a simple and arresting theme, supported by artfully selected research. In Makers and Takers he says that conservatives are, in their private behaviour, superior to liberals: “Conservatives work harder, feel happier, have closer families, take fewer drugs, give more generously, value honesty more and are less materialistic.” Liberals are narcissistic, selfish and grasping. They think benefit cheating is fine and prefer charities that campaign to those that actually help the poor. They sleep around, hate marriage and family and - “according to research carried out at Princeton University” - hug their children less. “My wife,” chortles the author, “thinks they're too busy hugging trees.”

Conservatives, meanwhile, are a benign cadre of honest Cheeryble brothers: giving to the poor, caring for their parents. Left-wing ideology corrupts, concludes Mr Schweizer on raising his head from “America's premier social research database”. He joyfully quotes Orwell's gloriously intemperate observation that “the mere words socialism and communism draw towards them with magnetic force every fruit-juice drinker, nudist, sandal-wearer, sex-maniac, Quaker, nature-cure quack, pacifist and feminist in England”.

Schweizer is no Orwell. There are in his thesis many vast ragged holes and wickedly selective statistics. If rightwingers are, for instance, less likely to throw a sickie at work than lefties, it may well be that they are older and have nicer jobs (Orwell, who always gets conscripted by both sides, also wrote that every intelligent boy of 16 is a socialist. Reverse that, as he did: the older you get the more you see the point of responsibility).

A lot of the book's research depends on self-description, and could equally well be used to say that people of right-wing views are apt to boast about their good qualities (“Do you get happiness by putting someone else's happiness ahead of your own?” is a typical question). Schweizer has a positive terror of feminists, joyfully quotes the nastier and nuttier left-wing bloggers, thinks the deeply eccentric Michael Moore is a typical liberal, and becomes ridiculous when, trying to prove that lefties hate children, he cites the “self-described socialist Ted Turner” who said that if he was doing it over again he wouldn't have had five “but I can't shoot them now they're here”. Come on, Schweizy - it's a joke. You know? J-o-k-e?

Good fun, though, and it is true that it has been too easy to caricature Tories as greedy bastards and the Left as soppy saints (why else does David Cameron fight the image by being so touchy-feely, and new Labour bang on endlessly about its toughness?). And there are grains of recognisable truth in the Schweizer thesis. I have long been puzzled by the fact that the British left-wing media house the most gratuitously spiteful, snarky columnists while weeping all over the front page about Africa, while rabidly conservative journalists often turn out to be personally kind and thoughtful. The wife of a man who writes like a Mussolini mini-me once told me: “Oh, darling, honestly, if X actually MET a homeless person he'd be apsley SWEET to him.”

There was a kind of truth in that. And as Schweizer says, the idea that the State should care for the unfortunate can “create a swathe of left-wing people who want to outsource their obligations to others”. In fairness he could also have mentioned the right-wingers whose Darwinian ideology tells them that unfortunate people deserve all they get, but you see his point. Statist egalitarianism does breed harshness: take the vendetta against private schools or the NHS policy that those who stakes their own money on an life-saving drug must then pay for ordinary hospital care. The principle “if the State can't do it for everyone, nobody shall have it” is a cruel one.

And indeed, sometimes it is the richest liberals who endorse this idea. Affluent lefties are an easy target: witness a recent glorious moment on Question Time. Polly Toynbee was soberly talking up green taxes and biofuels while the rightist rottweiler Richard Littlejohn cited the fuel and financial travails of ordinary people. Toynbee spoke disdainfully of his Daily Mail salary, as if that disqualified him from caring. Littlejohn shot straight back by asking whether she worries about poverty and the environment while flying to her private villa in Italy. The resulting facial expressions have been starring on YouTube ever since.

But Schweizer's one-sided polemic misses a wider, more interesting issue, which is the way political attitudes of any colour get used to exonerate personal nastiness. We are only human, and we love nothing more than an excuse. The fat cat on bonuses, or the super-rich media executive or MEP, will cite business theory about how “top talent” must get top money - even if, in the latter two cases, it is doubtful that the wider marketplace would ever actually want to hire a Kinnock or a moribund BBC mandarin. The sexually timid often use strict Christianity (or Islam) to justify their reluctance to give unstinting love. The Bible has been called in evidence to subjugate women,

Hindu theology to belittle the disabled, and biological sciences conscripted to justify racism. Darwinian-Thatcherite political phrases have veiled great injustices to the poor, and the rhetoric of the Left has excused massacres.

Just as importantly, every strong ideology offers a licence to loathe. A leftie can continue to feel pure while directing venom at huntsmen, boarding-school parents or Middle England. A right-winger can enjoy sneering at social workers, idle “chavs” and illegal immigrants, without ever attempting empathy. Muslim extremists love to loathe the kuffar, puritans exorcise their hangups about the body by thundering against even the most gentle and loving gay couples, gay crusaders sneer at the straight.

And none of this means that there is anything innately wrong with the Left or the Right, or religion, science or gay pride. The fact is that deep down we are all a bit nasty and selfish. When we use ideologies to camouflage what should be our shame, any belief will do. Mr Schweizer calls his book Makers and Takers. He should have admitted that every banner also shelters fakers, snakes and haters: unoriginal sinners all.

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