It's late o'clock on Saturday night. Dan, Chris and I have torn ourselves away from a sweaty Brick Lane party in east London and are loping towards the bus stop. We pass a group of three young men, and as we do, one of them extends a tentacle, slithering it over my arse. I say nothing until we're at a safe distance, then I tell the lads what happened. Chris is angry. He turns around and asks which one's the squid. I don't know, I didn't look, it's late, I'm tired, I really couldn't be bothered dealing with any aggro. Chris apologises if he's being paternalistic – it's up to me whether or not to do anything, of course. They're my friends and they're being protective, and protectiveness comes from a good place. I know, because, although it's not immediately obvious, I am being protective, too.

Here's Saturday's plot synopsis from my maternalistic perspective: three dodgy men are walking around east London late on a weekend. One of them wants a fight. He sees two men and a woman approach. What's a good way to set about getting his jollies? Exactly. And I'm not going to see my friends lose some teeth just because some slime-creature touched my bum.

Although protection of the opposite sex in public spaces is often taken to be a male prerogative, women often try to protect men from violence through quiet acceptance of harassment. If I'd been on my own last Saturday, I'd most likely have turned around and hollered horrors at squid-boy until his ink ran dry. By the time I'd finished telling fish-features how stinky he was, he'd have been begging for Oldboy to put him out of his misery. I'm confident behaving like this on my own because, while I'm likely to be groped in public (not even thick leg hair and Dunlop sandals can put some men off), it's a significant boon of femaledom that I'm pretty unlikely to be beaten up.

Sofie Peeter's recent controversial documentary, Femme de la Rue, allows us to walk in the footsteps of the film-maker and experience the sexual aggression she endures on a day-to-day basis. This is powerful: it helps apologists to see that street harassment is not complimentary, but disrespectful and often frightening. It seems as if women have been screaming this message for years, with campaigns such as Stop Street Harassment garnering significant public support. Yet squids still slither. Why? Peeter's film is set in Brussels, and not unproblematically it appears to frame street harassment as a clash between western and Islamic cultures. I don't live in Brussels, and I'm not going to pretend to be an expert on cultural tensions in that city. But I do live in London, and I'm pretty sure that the squids here don't think they can get away with tentacle tricks due to confusion over the social and sexual role of western women.

The vast majority of men who engage in street harassment in London are under no illusions that their advances are socially acceptable. So why do they think they can get away with it? As strange as it sounds, I think that part of the reason lies in the way men and women protect each other. Many men feel they should protect women from unwanted sexual advances, but unfortunately this ultimately produces negative effects. For example, the more men walk women home to protect them, the more the sight of a lone female in the streets attracts opprobrium. Erasing female presence in public spaces makes those spaces less female-friendly and impedes the mobility of all women in society. Similarly, a man's protective urge to square-up to a perpetrator may mean a victim is less likely to say anything next time.

But men, as I've mentioned, don't have the monopoly on protectiveness. Women often downplay street harassment because they don't want to upset their friends, ruin a good night out, or have their boyfriend beaten up. When women protect others from discomfort and violence by keeping stumm about harassment, they help to create a culture in which the perpetrator goes unconfronted.

If Dan and Chris thought that I didn't kick off on Saturday night for their benefit, they'd most likely be frustrated with my maternalistic thinking (too late now – it's in the Guardian!). Adults are capable of making their own choices when it comes to personal safety, and about how to react to aggression, sexual or otherwise. Thinking through all of this, I've come to the rather counterintuitive conclusion that by being a little less protective of each other, we might engender a society in which we need to protect each other less.