In the time old tradition of the supermarket Christmas advert, Tesco has stuck to a familiar formula: a stellar cast plays one funny family. In previous years, it was Prunella Scales and Jane Horrocks; this year, it's Ruth Jones, Ben Miller and Will Close.

One of this year's adverts, entitled Flirt, features the son, a man in his mid-twenties, following a woman around Tesco as she shops. Every time he attempts to engage her in conversation, she moves away. He follows her. She moves away. He follows her.

Compare this behaviour to that in the video for Transport for London's fantastic Report It campaign, encouraging women to report as a crime, ANY behaviour that makes them feel unsafe and uncomfortable, including the kind of behaviour in the ad.

I worked in my university library. There was a man who followed me as I stacked the shelves with books. He never spoke to or touched me. He just trailed behind me as I moved between aisles of books, staring at me while I worked. When I confronted him, he laughed. I reported him to security and he never came near me again.

One afternoon my friend, in the same library, looked up from her work to find a man masturbating while staring at her. She moved. He followed her. She went to security.

"It's a bit embarrassing," she began. "Don't worry love! We've heard it all before," they chortled. "There's a guy upstairs touching himself." "Say again?" "He was staring at me and touching himself. When I moved he followed me."

She told me that reporting the crime to these kindly, avuncular men, who were old enough to be our dads, felt as awful as the crime itself.

Last week, cabaret singer Lili La Scala was getting the last train home on a Saturday night, when she was approached by five drunk men. "You're beautiful." "You've got blue eyes. Blue's my favourite colour." "Are you naked under that coat?" "Stuck up c**t!" "Only havin' a laugh, innit?"

Since writing about her experience, hundreds of women have contacted La Scala to share their own stories.

She wrote: "Their pain, anger and humiliation has burned through me as I have read their words. Hundreds of women. Hundreds. How can this be acceptable in 2015? I have the right to travel home in silence. I have the right to travel home alone. I have the right to not make small talk with drunk men I've never met. I have the right to not be intimidated."

If you think I'm being over-sensitive about a silly Christmas advert, consider the above. Tesco is showing male entitlement as a joke, that women should passively accept and tolerate harassment in a public place, even when they repeatedly walk away from and refuse to engage with their harasser. At best it's tasteless and misguided, at worst it's dangerous.

Being a woman alone in a public space – a train, a library, a supermarket – carries a risk that some men will believe they are entitled to a smile. A conversation. Or that they're entitled to tell you they want to spunk in your hair – as someone reported to La Scala. If you object, you're a stuck up bitch and they were only having a laugh.

The tone of the Tesco ad is light-hearted, the character of the harrasser is foppish and unthreatening (he thinks Advocaat is wine! What a lovable doofus!). But stalking doesn't make me laugh. Pestered women doesn't put me in a festive mood. It makes me scared and sad. Next year, Tesco, keep the fantastic Ruth Jones. Get rid of her creepy son.