I once worked with a woman whose conversational style was to disagree with everything I said. One day she remarked, "It's a nice day outside." I said, "Yes, it is." She said, "Not really. It's kind of crappy outside."
I don't think she was even aware of her behavior.
I've come across other people like this before, but I never thought much about it until I read this post by Gretchen Rubin, author of The Happiness Project:
Here’s a new phenomenon I’ve tentatively identified: oppositional conversational style.
A person with oppositional conversational style is a person who, in conversation, disagrees with and corrects whatever you say. He or she may do this in a friendly way, or a belligerent way, but this person frames remarks in opposition to whatever you venture.
I noticed this for the first time in a conversation with a guy a few months ago. We were talking about social media, and before long, I realized that whatever I’d say, he’d disagree with me. If I said, “X is important,” he’d say, “No, actually, Y is important.” For two hours. And I could tell that if I’d said, “Y is important,” he would’ve argued for X. I saw this style again, in a chat with friend’s wife who, no matter what casual remark I made, would disagree. “That sounds fun,” I observed. “No, not at all,” she answered. “That must have been really difficult,” I said. “No, for someone like me, it’s no problem,” she answered. Etc.
Since those conversations, I’ve noticed this phenomenon several times.
Over 190 have commented about this on Gretchen's site.