"Alright, let's keep some dignity going. You're normally some kind of sentient humanoid, probably, right?" Sure, being in certain shapes does some funny things to the brain. Whenever Taako's a dinosaur, for instance, his intelligence suffers. The difference is that he's the one in change and the transformation is held in place by concentration, so it's always easy to let go. Either way, ferret instincts are not of interest to him and he doesn't feel like having a squirmy little weird thing poking him. If he was cool with that he'd be much nicer to his apprentice.