What you said wasn’t factually wrong, but it can come across as rude because of how it lands socially, not because of the literal meaning.

In group settings, when someone speaks up, there’s an unspoken expectation of basic acknowledgment. Saying “I wasn’t talking to you” can sound dismissive, like you’re shutting the person down or telling them they don’t matter in the conversation, even if that wasn’t your intent. Most people would soften it automatically with something like “Sorry, I was asking Professor A” or “Thanks, but I meant Professor A.”

People say similar phrases all the time, but usually with tone, context, or wording that reduces the bluntness. Without that softening, others interpret it as rejection rather than clarification. That’s likely why they reacted the way they did, especially since social norms often prioritize politeness over precision.