I was recently out at a bar on a Sunday afternoon. The couple next to me (who I’m not sure were actually a couple – the woman kept saying to the man, “You’re my best friend”) were having a heated discussion over a bottle of wine. Maybe they were a bit drunk. All I know is it was so awkward sitting next to them that my friends and I, and a number of others, swiftly moved from the table, despite the bar being packed. We resorted to sitting on a wall next to them but, unfortunately, still in earshot.

They were arguing about feminism and clearly the guy didn’t agree with her. I found it hard to listen to – he was completely disrespecting her. He kept calling her ideas stupid, and would say, “Can you understand how stupid you sound?” He denied her version of the world. When she talked about feeling held back as a woman he ridiculed her, asking who was holding her back and how, saying maybe it was just her own fault. It’s not that I have a problem with scrutinising what someone says, it just felt like he wasn’t listening to her, he wouldn’t even let her finish.

Even when she began crying and talking about an abusive relationship with her father, I felt he began emotionally manipulating her and reducing her feelings. She spoke about domestic violence she had experienced and said women walk around carrying the fear of rape and murder with them. But he turned it on her, saying things like, “This is just as bad for men. I can’t believe you think it doesn’t hurt men to live in a world knowing rape happens.” Eventually she broke down in tears again, but he started telling her she was angry because he didn’t agree with her and she couldn’t just cry whenever someone didn’t share her point of view.

These sound like little things and I feel stupid writing them down, but that’s part of the problem. What he was doing was so clever and subtle that it was hard to put your finger on. I felt he was being manipulative – not listening but undermining and patronising her. (It was interesting, for example, that he pressed her to provide “proof” for what she was saying, even though she worked in data and offered up personal experiences.) It felt like bullying. Sometimes he insulted her and diverted the conversation to himself whenever she tried to share her experiences, accusing her of not focusing enough on him.

During the whole conversation I was with two friends. I kept saying I wanted to say something, to assure her she had people on her side and didn’t need to put up with being spoken to like that. But they said I should mind my own business. I know what I saw was abusive and feel that if this guy was hitting her, we would have jumped in. But for some reason we couldn’t challenge what was going on – a whole bar of people standing around them in the middle of the afternoon.

I want to know what people should do in these situations. Should I have told him he was being a bully? Should I have told her she can do better or that I didn’t find her ideas stupid? Would I have made it worse by getting involved? And was what I was seeing actually abuse?

This is tricky. Sometimes “mind your own business” can sound very similar to “it’s not my problem”. On the other hand, we should be wary of getting involved in others’ business, because we don’t know the context of their situation or whether we will be a help or a hindrance.

This man’s behaviour sounds insidious, so much so that even you doubt your own verdict. I can’t imagine what it was like for her. His behaviour carries all the signs of emotional abuse, which can happen in non-romantic relationships, and can involve constantly putting someone down, humiliating them in public and cutting them off or not listening.

But intervening might be unhelpful. “We see a lot online these days about the bystander effect, encouraging people to intervene, for example, if they see sexist or racist abuse,” says Laura Dix of Women’s Aid. “But intimate relationships are different: you don’t necessarily go home with the person being racist or sexist to you in the street, but you do with a partner.”

If the situation escalates to being threatening, violent, or putting someone at risk, you should of course call the police. But otherwise, consider whether intervening will be safe for you, and whether it will be safe for the person you are intervening on behalf of. Many people who experience abuse feel embarrassed or ashamed of it, so pointing it out in public might not gain the reaction you expect: “She might not be receptive. She could be defensive of the guy, or even angry. In abusive relationships, people need to protect themselves however they can,” says Dix.

We can pull the focus away from the person experiencing abuse, instead breaking the silence on abuse ourselves. Women’s Aid run a programme called Ask Me: “It’s about encouraging people to speak up in their own communities, perhaps talking to friends about everyday examples of abuse they may be seeing in popular culture – like on TV, as has been done recently around programmes such as Big Brother and Love Island; not necessarily in a combative sense, but offering an alternative worldview.”

• What do you think? Or have you got a question for Poppy and readers to consider? Post your responses below or email them to in.it.together@guardian.co.uk