If you’re in that situation when someone talking to you starts to “vent” about someone else… it usually starts small about how hard things are at the moment… but in order to explain how they’re feeling, they feel the need to share how this person has wronged them and that person was mean to them… and before long you’re hearing things that you ought not to hear… what should one do?
It’s a difficult moment, because you’re hoping that at any moment they’re going to recognise what they’re doing, you’re hoping they’re going to realise they didn’t mean to go into all that, and stop all by themselves. But… I think that’s very rare.
You should politely ask them to stop. Maybe…
“Can I stop you there for a second? I wonder if you’ve started talking about people in a way you wouldn’t like people talking about you?”
“Can we just press pause on this conversation for a minute? It sounds like you’ve got a lot of feelings rolling around at the moment and you might not have thought hard about what you should and shouldn’t say?”
But stopping it is only part of the response. Ideally, you want to help this person work out WHY they came to you in the first place… Did they really just want vengeance (and thought you knowing might help)? Are they simply trying to process what happened to them and their feelings and facts are getting all muddled up? Do they want you to go and fix their problem? Have they already had the same conversation with 5 other people (who didn’t tell them to stop) and now their just in the habit of talking that way?
Once again… it’s very rare that the presenting issue is the real issue. So try and treat the cause, not the symptoms.