"Odd. I'd recommend certain charms you can use to avoid those nasty bezoars. But apparently it's too late. Doesn't say much for your being a professor, does it?" There was an edge of a smirk to his smile, now. What could she do to him? Detention? Points? Send him away to the Headmistress for punishment?
He had to keep up appearances here, and baiting the mudblood loving, scratched out lines of his family tree would certainly do that.