This is so bizarre. I would show a huge lack of empathy as well.
But I agree with you that "I can't continue this conversation" is probably not the best way to respond, even in that case.
If you don't care about the person and their emotions, don't say anything. Nobody else will know otherwise (other than the person you clearly don't actually care about). Feigning care is sometimes worse than just clearly not caring at all.
Most people have reasonable expectations about how much care they can expect from some random colleague from a past project.
And the limit is just engaging with someone in a way that they didn't ask you for, and in a manner that doesn't serve them at all?
> Most people have reasonable expectations about how much care they can expect from some random colleague from a past project.
The context here is a person who was just let go. Like, not an old buddy from a previous job.
Maybe it's the New Yorker in me, but if you're not going to serve a purpose, emotionally, financially, physically, etc... mind your own business.