"All I want for Christmas … is an end to the mandatory gendering of every children's toy!" Mariah Carey didn't sing. Though if anyone could cram that many syllables into a phrase of music, it surely is Mariah. The person singing this particular affront to seasonal pop is me, and I must have been an awful good girl, because Santa has already given me what I want. Except, instead of being attended by a round ruddy man in clouds of beard, my chimney has been visited by the entire country of Sweden. Nice one!

In 2009, the Swedish equivalent of the Advertising Standards Authority sanctioned retailer Top Toy for producing a catalogue that "preserved an anachronistic view of the sexes" and showed both sexes in a "disparaging way". So this year, the company has responded with advertising designed to confound every gender prejudice. Behold: a girl … with a Nerf gun! A boy … holding a doll! A girl … in a blue T-shirt! Eat it, patriarchy.

The amazing thing is that gender roles for children have become so calcified that such petty things can be presented as radical. Sample headline from the Daily Mail: "Dolls? They're not just for girls", which of course relies on the voice of your inner Ukip voter shouting, "YES, dolls are just for girls!" to get the reactionary sap rising. Has the Mail secretly signed up to a lesbo-matriarchy where children are reared by women only? Has it gone cold on the need for fathers? It seems unlikely, but if boys can't play at childcare, then by extension we're saying they can't grow up to care for children.

Play is how children practice belonging to the world they've been born in. Dolls let infants rehearse the care they'll give to their own infants in turn, and imagine themselves into the feelings of their own parents – the ability to second-guess mum and dad being second only to the ability to destroy expensive consumer electronics in a preschooler's skillset.

A lot of people will try to tell you that boys just don't like playing with dolls. Coincidentally, these same people also tell any boys in their vicinity that boys don't play with dolls. It's not innate sexual difference that makes girls and boys play either side of the pink-blue divide – it's adults constantly impressing on their charges that one group of toys is right and the other is wrong.

This pressure can be as subtle as the involuntary "ooh!" of applause for a child picking the "correct" toy, or it can be as blatant as the teacher from Chicago who had pupils categorise toys as boys' or girls' for a sorting exercise, then failed an eight-year-old girl for putting most things in the "both" column ("wish she had failed it even worse," tweeted the girl's proud, awesome dad.)

I was determined to give my first child a beginning free from gender dogma, so it was both brilliant and slightly blindsiding when, aged three, his Christmas list led off with a baby and a buggy (I found him one upholstered in blue, of course. The gender police have spies everywhere, even inside me). I was helped out by the fact that I was a student at the time, and my son went to the university nursery where a lot of the other parents were thoughtful, right-on lecturer types who raised their children on dungarees and wooden toys.

But even thoughtful, right-on lecturer types have TV, visits to toy shops and slightly less thoughtful and right-on family and friends: the pink pox couldn't be kept out forever. It seemed to arrive in the space of a single week, a preschool room of stripy T-shirts and denim half-erupting in tiaras and princess dresses. Us parents had enjoyed a good run, but our children had finally twigged that greater forces wanted them to conform to a certain pair of types.

At first, my reaction to this was one of cynical resignation – of course we couldn't win against the massed forces of Disney and Mattel, so why had we even tried? I've changed my mind now. You can't resist the gender sorting hat for ever, but you can give children a start that shows them the gender sorting hat isn't a natural and inevitable part of being human.

That's why Top Toy's catalogue is good news for Swedish kids: when someone next tries to insist that girls play one way and boys play another, these children will have a picture in mind that tells them otherwise. And that's why every time my second child, a girl, shoots me in the face with the Nerf gun that she demanded for Christmas, I remind myself that this is exactly what I asked for.