When Rooney Mara, star of The Girl With the Dragon Tattoo, suggested that Lisbeth Salander was not a feminist, Stieg Larsson's partner knew how to put her down. "Does she know what film she has been in?" asked Eva Gabrielsson, who shared much of Larsson's life until his death in 2004. "Has she read the books? Has she not had any coaching?"

In case you were in any doubt, the questions were rhetorical. To Gabrielsson, Mara was another ignorant Hollywood star. If she had taken the trouble to understand The Girl With the Dragon Tattoo before playing its goth heroine, she would have realised that Salander's "entire being represents a resistance, an active resistance to the mechanisms that mean women don't advance in this world and in worst-case scenarios are abused like she was".

Her repetition of "resistance" flagged that Gabrielsson, like Larsson, had done time on the European far left. Their backgrounds only emphasised the extraordinary and apparently admirable success of the Millennium trilogy. The far left's record on women's rights would make the Vatican blush with shame. Its alliances with radical Islam make it, at best, a misogynist force and, at worst, an active agent of oppression. Larsson appeared to be the exception. I wrote in the Observer about how impressed I was when I discovered that while completing his thrillers, Larsson found the time to dash off a polemic about honour killings in Sweden. Here, after all these years, was a leftist who preferred to drag himself out of the swamp of relativist politics rather than compromise his principles.

I won't pretend that the novels are feminist tracts. Like most thrillers, they rely on plots that strike you as absurd as soon as you stop turning the pages. Salander may be a victim of rapists to begin with, but she becomes a superwoman, taking on and beating Hell's Angels and emptying the bank accounts of a corrupt plutocrat without the police suspecting her for a moment. Mikael Blomkvist, the shabby, middle-aged journalist who helps Salander, is a politically correct Don Juan, so charismatic that he does not even need to try to persuade a procession of beautiful women to join him in bed. As I and every other shabby, middle-aged journalist at the Observer can attest, Larsson's fantasy is not an example of art imitating life.

For all the surrounding silliness, feminism holds the story together and gives it a strange power. The persistence of the abuse of women by men, and men's expectation that they can get away with it, explains the novels' crimes and the determination of the heroes to solve them. There is something truly thrilling in the notion that the bestselling thrillers of the past decade were written by that modern rarity – a leftwing, male feminist.

Except that Larsson wasn't a feminist – or not a consistent one. He wrote with real anger about the oppression of women with white skins. When others tried to do the same about the oppression of women with brown skins, he denounced them as racists. My friend and colleague Johan Lundberg, the editor of the Swedish journal Axess, has done what I should have done and read Larsson's obscure book on honour killings. He waited for the release of the film to give us his findings.

Larsson did indeed break off from writing the Millennium trilogy to intervene in the debate about the "honour killings" of two Kurdish women in Sweden. Far from worrying about the suffering of women, Larsson and his co-author said those who campaigned for the rights of women in immigrant communities wanted "to portray all male immigrants as representatives of a single homogeneous attitude towards women". They had sexist as well as racist motives. They only talked about honour crime because they wanted to divert attention from how white men raised in the "patriarchal structures of Swedish society" abused and murdered women as a matter of course.

If all Larsson wanted to say was that the rights of women should be upheld, regardless of colour or creed, then no one could argue with him. He came close to asserting the opposite. Believe that western legal systems, for all their faults, were preferable to forced marriages, religious courts where the testimony of a woman is worth half that of a man and the stoning to death of adulterous women and you were a "rightwing extremist", carrying on the fascist tradition. In a final descent into paranoid dementia, he accused those who disagreed with him of preparing to unleash "special operations forces, which are ready to begin the ethnic cleansing".

Read the trilogy or watch the film and you can trace Larsson's beliefs by his errors of omission. He includes every variety of male violence against women, except the violence inspired by religious and cultural misogyny. I do not wish to be too priggish. A work of art – high or popular – lives or dies on its own merits. Larsson was also a brave man, who faced down death threats from Scandinavian Nazis. That he could propagate brutish ideas in his political pamphlets on occasion does not change his anti-fascist record or invalidate his fiction.

His views would not matter if they were confined to Trotsky cults. Unfortunately, the notion that anti-racism trumps feminism is everywhere in the European liberal mainstream and has an especially tight hold on the British liberal-left. Its adherents are so frightened of taking on conventional wisdom they do not notice that they are behaving like the racists they profess to oppose. Last year, members of the British Iranian and Kurdish Women's Rights Organisation, which is not made up of the "rightwing extremists" of Larsson's conspiratorial imagination, provided details of thousands of threats, abduction, acid attacks, beatings, forced marriage, mutilations and murders men had inflicted on Muslim and ex-Muslim women. If the victims had been white, the left would have gone wild.

Our centre-right government would have never dared cut funding to women's refuges. Liberal opinion would have demanded that the police make tackling "honour" violence a priority and accused chief constables of sexist prejudice if they refused. As the victims were British Indians, Bengalis, Pakistanis, Kurds, Somalis, Arabs and Iranians, a nervous silence descended. Too few were willing to endure the accusations of racism from Stieg Larsson's successors a consistent defence of women's rights would have brought.

I do not go to actors for political advice. But when Rooney Mara said that she did not think that Larsson's Salander was a feminist, she was not the empty-headed celebrity she seemed.