I don't think I have very much in common with the average Daily Mail reader, but of the long list of public outrages that commonly feature in that newspaper, I confess that one in particular succeeds in striking a chord: the "rights culture" that has taken hold of modern Britain.

More than once I have caught myself tut-tutting that there is too much emphasis on "rights" and not enough on responsibilities; I feel flashes of rage at stories I hear from teachers about their pupils, ignorant of almost everything except their "rights" which simply serve to undermine the teacher's authority; once or twice, I have even pronounced that "people need to start being a bit afraid again, and realise that unless they pull their socks up life will be far from a picnic".

Watching Clint Eastwood's new film Changeling is a useful antidote to this branch of hardening Right-wingery. For the world it portrays, in prohibition-era Los Angeles, is a world without rights at all. It is a world where those in power are free to bully and connive and lie with impunity and where whole swathes of society are powerless to defend themselves. As a matter of course, women are bullied and harassed by men, people on the fringes of society are killed and beaten by a corrupt and brutal police force and good people go about their lives in a constant state of fear.

On the evidence of Changeling, maybe being afraid isn't such a winning formula after all, and maybe rights are rather wonderful.

Angelina Jolie plays Christine Collins, a single mother abandoned by her husband who these days would be held up as a shining example of good, responsible living. (Well, if she looked like that, these days she would be an actress or a pop star - a typically overglamorous casting but I can't say I minded.) She works hard at the local telephone exchange, where she has become junior manager; she puts all her remaining time and resources into bringing up her beloved son, Walter (to whom she is very close), and she keeps a tidy and respectable home within her modest means. Her life isn't much fun, but she loves her boy.

Now imagine the worst possible series of bizarrely vindictive turns of fate against this woman, and you have the plot of Changeling. It also happens to be a true story. First, she is summoned in to work an additional shift she wasn't scheduled to do, and returns home to find that Walter has disappeared. She rings the police and is told that they don't investigate cases of missing children until at least 24 hours have elapsed - already the presumption is that, as a single mother, she is not to be trusted.

After five long months the incompetent police department, suffering from bad news reports in the press, announces that they have found the boy and in a highly photographed press event she is "united" with her child. Except it is not her son - they have found a random street boy from Illinois who looks a bit like him, and when she protests after the photoshoot, they insist she take him home.

For weeks after, despite her protestations that the child is three inches shorter than Walter and is even circumcised, the police do not want the hassle and bad press of suggesting they have made a mistake. Only the Rev Gustav Briegleb (John Malkovich), an eccentric community campaigner, believes her and begins to attract publicity to her cause.

The chief of police decides she is becoming a public menace and has her forcibly despatched to a mental asylum on the grounds that she is clearly mad not to recognise her own son. The asylum is full of women who have been removed for convenience by the authorities, and they undergo horrific torture, including (in scenes so awful they are hard to watch) electric shock "therapy".

As if life was not bad enough, the news then emerges that a serial murderer has been found who had chopped up over 20 children with an axe, and Walter is thought to have been one of them. There is then a whole final third with codas and sub-codas, trials and hangings, new last-minute characters and much more dreadfulness.

You will recognise that, as far as movies go, this is a weird and sadistic plot. Enjoyable it is not. The plot is so over the top that about halfway through it begins to unravel. After so many stages, thick with pain and violence, it begins to lose coherence and just becomes plain depressing. "Enough already," you cry, "I get the point! I am sorry for agreeing with the Daily Mail! I love the rights culture! I take it back!"

That lesson is the redeeming feature of a flawed and not terribly good film. Christine's case becomes a landmark moment when society rises up against unchecked power, and the voiceless begin to be heard. But don't look at those giant posters of Angelina Jolie's lips, currently plastered all over the London Underground, and think Changeling is a sexy thriller, or a must-see for a Christmas season night-out. It is horrible and it is penance even you don't deserve. Just leave off the Right-wing tabloids for a while instead.