I suspect Gillian meant he just expects Mully to behave like a dog - tell a dog "No" and they look guilty, furtive and apologetic. Tell a cat "No" and they'll enquire why, then theorise with you for twenty minutes while blatantly demonstrating how superior they are to us.
My OH used to go mad with Mac and Ross if they brought home mice and voles and stuff. He thought shouting at them and waving his arms around would make them stop. It didn't - normally all it meant was they dropped the (usually live) offering in affronted shock, which then meant it would take up residence under the nearest piece of heavy furniture, or alternatively they'd scamper off with it clamped in their jaws at high speed, looking indignant.
Finally - finally, I managed to persuade him that admiring the offering, asking if he can have a closer look, and distracting the gift-bringer, works far far better, and sometimes means live offerings can be returned safely to the outside relatively unscathed by the encounter.