"That's not true."

Today I arrived at my D&C class... only to realize that everyone was moving rooms, due to a very repulsive smell. In our new class, people coming late were asking why we'd switched rooms. Martha said, "the old room smelled like somebody stepped in poop". Then I said, "yeah, it smelled like dead people". Then this guy in front of me, who was very awkward looking indeed, turned around to face me and said, "that's not true", like I really thought that it smelled like dead people, and in a voice making himself out to be an expert.