Misogyny is like a virus. It can be fatal – something I realised when I covered the Yorkshire Ripper murders in the late 1970s. It has the capacity to mutate, which is why I wrote a book called Misogynies in the plural. And it is infectious, which is why public life is so toxic for women at present.

Just think about it. Last month an inspirational Labour MP, who also happened to be the mother of two children, was shot and stabbed in her constituency. The murder of Jo Cox rightly caused an outpouring of emotion, from shocked disbelief to calls for more civility in public discourse. But memories are short, especially in the feverish atmosphere of a Labour leadership contest. I could hardly believe my ears when Owen Smith, in a campaign speech about equality, said he was upset that Labour did not have the power to “smash” Theresa May “back on her heels”.

Smith’s careless use of language is not just offensive to women who have painful memories of domestic violence. In recent weeks, the Labour MP Angela Eagle has had a brick lobbed through a window at her constituency office. She has received a torrent of abuse, including death threats. Her colleague Luciana Berger has contacted police after being sent a picture of a kitchen knife and a message telling her that she was going to “get it like Jo Cox did”.

I have never known a time when woman-hating has been so seething or so widespread. When Misogynies was published in 1989, I believed I had identified something that was on the way out. I was angry when I wrote the book, mainly because it wasn’t long since I had witnessed the hopeless police investigation into the Yorkshire Ripper murders at close quarters. Between 1975 and 1981, Peter Sutcliffe killed 13 women, while the police chased after a hoaxer who taunted them on an audiotape. After years of nightmares, I realised that the murders were part of a wider and age-old phenomenon.

Researching the book, I found plenty of evidence of misogyny, from Roman poetry in the first century BC to Page 3 of the Sun. But it was bearable because equality legislation was coming thick and fast and job opportunities were opening up for women. I counted myself lucky that I had missed out on witch trials and the selling of captured women into slavery. I never imagined that, all these years later, that I would begin to see photographs of men with long hair and straggly beards in Syria, crammed into the back of trucks under a sinister black flag. It is hard to believe, but if I were writing Misogynies today, I would have to include a chapter about Yazidi girls being sold in slave markets in the Isis stronghold of Raqqa. Or Boko Haram, a terrorist organisation so implacably opposed to girls’ education that it kidnaps Nigerian schoolgirls and forces them into sexual slavery.

Woman-hating has come roaring back, borne on a tide of recession, economic uncertainty and religious extremism. In this country, we have just witnessed misogyny in its “jokey” form, prompted by May’s arrival at No 10 Downing Street. “Heel, Boys” declared the Sun, showing a pair of kitten heels trampling on the heads of six of her most senior colleagues. Haven’t you got a sense of humour, love? It revived memories of an old trope of Margaret Thatcher as the Conservative party’s dominatrix, confirming that some people cannot see a woman assuming power without thinking of men being humiliated.

Tragically, the presence of women in powerful positions seems to unleash misogyny rather than curb it. Hillary Clinton’s first attempt to win her party’s presidential nomination was accompanied by a campaign of breathtaking nastiness. Last week’s Republican convention ramped up the misogyny with witch-hunting chants of “Lock her up!” Angela Eagle’s courageous bid to challenge Jeremy Corbyn ended when more of her colleagues backed Smith, a man with much less experience. Anyone who thinks Eagle’s campaign was flat should bear in mind the fact that she was receiving so much abuse that her constituency staff had to take the phones off the hook.

Misogyny has deep roots. It sometimes becomes dormant – usually when the economy is doing well – but it never really goes away. It is a mistake to regard it as just another form of abuse; it is a peculiarly intimate form of hatred, rooted in relationships carried on behind closed doors but that frequently spill over into the public world. (Racists rarely marry their victims but misogynists often do.)

It needs to be met with zero tolerance, because once it starts being culturally sanctioned, there is no end to it. When a well-known woman starts receiving rape threats on Twitter, hundreds of other people join. In a more extreme example, the prohibition of rape has been abolished in areas of Iraq and Syria occupied by Isis, attracting recruits who like the idea of having coercive sex with 14-year-old girls.

Misogyny flourishes when politics become polarised, for a simple reason: it is as prevalent on the hard left as it is among religious extremists. Look at the number of supposedly radical men who rushed to defend the WikiLeaks founder, Julian Assange, when he faced accusations of sexual assault and rape in Sweden. Some of them are still batting for this narcissistic misogynist, four years after he became a fugitive from justice in the Ecuadorian embassy in London.

A day after Jeremy Corbyn’s election as Labour leader, the three great offices of state in his shadow cabinet were given to men. It came as no surprise to feminists, who know that the hard left rarely pays more than lip service to a movement it regards as a distraction from the struggle against imperialism. Nor am I surprised that Labour has become a poisonous environment for women MPs. Last week 45 of them signed a letter to Corbyn, demanding that he do more to stop harassment, vilification and intimidation.

I have watched these developments with outrage – and a weary sense of deja vu. Many brave women died for freedoms that are under attack once again, all over the world. And I am as offended by people who play down outbursts of misogyny as I am by those who unashamedly revel in it. After the murder of Jo Cox, I don’t want to hear anyone telling worried female MPs to toughen up or whining that they have received death threats, too.

Woman-hating should be a nasty anachronism, but it’s back and we have to confront it. I know what I’m talking about: when it comes to misogyny, I really did write the book.