He has a point. In Buffy's experience, it's been true that those most vocal when proclaiming their innocence are usually the ones with the most to hide. And in this case, technically, he isn't wrong. She is trying to cover up for the fact that she was kind of, sort of stalking him. For his own good! But stalking nevertheless. Not that any of it matters at the moment. There are larger, ickier matters to be dealt with.

She's about to shout that yes, she names things all the time, and in fact her lucky stake is named Mr. Pointy, thank you very much, when the parasite moves in the bucket, sloshing around in that foul smelling liquid, and she remembers why she started screaming in the first place. "You're riled up? I'm riled up! Why are you carrying a parasite around in a bucket? And aren't parasites supposed to be, like, microscopic?"