Takes controlled thought to pick up an object and use it as a tool to smash something. I agree the snake boiling is the worse offense - due to the situation and means of dispatching, I'm not putting less value on the life of an invert per se - but smashing something with a book isn't an uncontrolled, fearful, reaction. If he had smashed the tarantula with his hand then I could probably buy into the fearful, uncontrolled, reaction. I think he acted rashly in the heat of the moment but could just have easily walked away. Heck, walking(or rather, running) away would have been the easier choice if he was truly afraid.