Meh...it's all showmanship. The audience wouldn't be nearly so entertained by placid animals. And I do believe Nigel didn't intend to walk out with a bleeding neck...I'll bet it happened right when the curtain was about to open and he couldn't do anything about it. When he sits down, he reaches around to feel it and looks surprised that he's bleeding.
Taunting someone with snappy snakes isn't exactly good diplomacy for the reptile-keeping world, though...and I surely wish Nigel could have come up with a better way for his animals to be "entertaining".