What humor arise out of Higgins telling Eliza to limit her conversation to two topics?

The humor arises from Higgins assuming control over Eliza's speech and imposing arbitrary restrictions on her conversation. It highlights his overbearing nature and disregard for Eliza's autonomy, while also revealing his tendency to prioritize his own comfort and preferences over her well-being. This control and manipulation in their dynamic adds a comedic element to their interactions.