Even if you didn’t know what a “terf” was when the word prickled into national news reports a couple of weeks ago, you would probably have grasped from the context that being one was a Bad Thing. After a confrontation at Speakers’ Corner on 13 September between a group of feminists and a group of trans activists, the Sun headlined its report: “Fight breaks out during TERF ('Trans-Exclusionary Radical Feminists') protest in Hyde Park”. In the Mail, it was: “Members of the Action for Trans Health (ATH) clashed with their bitter enemies the Trans-Exclusionary Radical Feminists (or so-called TERFs)”.

As the brackets suggest, “terf” isn’t yet familiar enough to be used in the mainstream press without glossing, but it’s getting there. Those who use it claim it’s a neutral, descriptive acronym for a group that holds a defined position – that is, radical feminists who exclude trans people. That doesn’t wash with others, who argue that in practice it functions as a term of abuse, and point out that no one actually self-identifies as a “terf”.

In a detailed and even-handed blog post, the linguist Deborah Cameron has concluded that, “Terf does not meet all the criteria that have been proposed for defining a word as a slur, but it does meet most of them at least partially”. But significantly, she added this: “Terf is now being used in a kind of discourse which has clear similarities with hate-speech directed at other groups (it makes threats of violence, it includes other slur-terms, it uses metaphors of pollution)…”

If you’d been at Speakers’ Corner on 13 September, you’d have seen that discourse in action. As a group of women gathered in Hyde Park for an event called “What is Gender: The Gender Recognition Act and Beyond”, they were met by protestors who chanted “When Terfs attack, we fight back!” (At this point, it’s worth noting that the “attack” consisted of trying to hold a meeting.)

One of the women there for the “What is Gender” event was 60-year-old Maria MacLachlan. Janice Turner of the Times was also there. Here is her account of what happened next:

“So at Speakers’ Corner trans activists and feminists were chanting and taunting each other. Maria was taking photographs when an opponent grappled with her, snatched her camera and smashed it on the ground. Then a tall, male-bodied, hooded figure wearing make-up rushed over, hit her several times and as police arrived, ran away. I asked a young activist if she was OK with men smacking women: ‘It’s not a guy, you’re a piece of s*** and I’m happy they hit her’, came the reply.”

The violence is shocking, but the immediate justification of it is somehow even more so. While Action for Trans Health London said it condemned violence against women, the Edinburgh branch issued a series of uncompromising tweets stating that “punching terfs is the same as punching Nazis. Fascism must be smashed with the greatest violence to ensure our collective liberation from it”, and “violence against terfs is always self defence” (it also accused the London branch of "undermining" its stance).

In other words, there is a fringe of people who think it is OK – more than OK, laudable – to hit a 60-year-old woman if she thinks the wrong thing, because thinking the wrong thing is understood to be an act of aggression in itself.

And it is women specifically who elicit these vicious reactions. In November last year, the fundamentalist campaign group Christian Concern held a conference in London on trans issues called “The New Normal: Tackling Sexuality and Gender Confusion Amongst Children and Young People”. Among its speakers were a former Ukip candidate who had been expelled from the party for homophobia, and a therapist who claimed to be able to counsel people out of same-sex attraction. “The New Normal” was openly publicised and easy to access. It went off without disruption and unprotested.

In other words, it’s possible to espouse the most virulent prejudices about trans people without attracting backlash, so long as you’re not a feminist. On the other hand, if you are a feminist, the bar to being called a “terf” is remarkably low. Woman’s Hour presenter Jenni Murray achieved it by writing an article in which she pointed out that someone born and raised male will not have the same experiences of sexism as a woman; novelist Chimamanda Ngozi Adichie likewise made the grade by answering “transwomen are transwomen” when asked whether she believed that “transwomen are women”.

Even those who criticise the use of the word “terf” now often accept that it had a good-faith intent at one time, and has been a victim of mission creep. But from its very first appearance, it has functioned to blame feminism for male violence against trans people. In 2008, a blogger called Tigtog introduced it to mark the distinction between her trans-inclusive feminism and feminism that was specifically focused on the rights of people who are assigned female at birth. Of some comments by radical feminists, Tigtog wrote:

“The contempt just drips from every pixel (eta: of those comments), and why exactly? Isn’t that sort of contempt and disgust exactly what led to Allen Andrade beating Angie Zapata to death when he found out (through an act of sexual assault) that she wasn’t a born-woman?”

Allen Andrade, in case you hadn’t guessed, is a man. An extremely homophobic man, as his trial for the murder of Angie Zapata heard. There was no suggestion that he was influenced by, or even aware of, radical feminism in any form. Yet Tigtog, at the moment she coins the word "terf", seems to imply that the women who criticise male violence (radical feminists) are ultimately responsible for the violence that men commit.

In 2003, the UK government began a reform of sentencing for what were crassly called “crimes of passion” – cases in which a man had killed a woman, but claimed in mitigation that his victim had provoked him through her unreasonable behaviour. The feminists who had campaigned to change the law referred to this defence with grim humour as the “nagging and shagging” defence.

In the word “terf”, the “nagging” defence has been informally reprised, with female truculence defined as a kind of metaphorical violence that can be answered in literal kind. And as the word is accepted, so too is its internal logic that if a certain kind of woman is hit, it must be because she deserves it.