It seems like if the statement is literal, then it’s self-disproving, since the person cares enough to say that, and the person who they were saying that to cared enough to say whatever they said or did prior. Also the likelihood of no one (as in, no human I guess?) caring about what they had to say seems very low, and chances are a large number of other people probably would care, too.

If the statement isn’t literal but more rhetorical, then I’m not sure what it means, but I suspect it basically just means “I don’t care” (as in the person who says “No one cares” doesn’t care themself and wants to express this in a way that seeks to hold more weight by asserting that all other people feel the same sentiment as them, even though arguably they demonstrably care somewhat if they went out of their way to say that, I guess depending on effort required, or perhaps didn’t care originally but then developed some degree of care as a result of the annoyance they felt at being exposed to something)… or maybe it just means “I don’t like what you said/did” or “I’m annoyed by you”… alternatively it could mean “I think you’re stupid/worthless”, “I disagree with you” or “I don’t want you to speak/speak about this again”, or similar.

Anyhow, what is the most appropriate way to respond to this? It seems like an emotionally charged statement that warrants, perhaps being completely ignored, or maybe a measured response seeking to find some understanding or common ground, though a witty retort could be appropriate if respectful (I don’t believe 2 wrongs make a right, unless the first wrong somewhat necessitates the second, if that makes sense). That said, I’m open to hearing any kind of replies that might be given, regardless of how cordial/civil (or not) they are.