Because it's applying the terminology of scientific discourse to casual conversation, kind of like nitpicking a minor spelling, typographical, or grammatical error and using that as an excuse to negate an otherwise substantive comment.

Demanding a certain level of precision when the loose terminology isn't being used in bad faith comes off as an attempt to exert control over the terms of the conversation like a teacher or debate judge. It's insensitive at best and obnoxious at worst.

Obviously if the conversation is an actual legal or scientific debate precision and rigorous consistency are more acceptable, but that's by mutual agreement of all participants.