...and if the little rodent somehow gets loose during the flight (because, e.g., this ditz takes it out of the box to stroke), and can't be found / retrieved - why, I'm sure that you wouldn't mind being held personally liable for the cost of evacuating the aircraft and grounding it until the little dickens can be recovered, would you?
Regards,
People have brought small pets on planes before, got loose and no biggie. Once a scorpion was found on board but the plane still continued to its destination. The passenger would have been told to do not open the box, period.