I think a big problem when it comes to this debate is the fact that humans do not readily rely on their instincts anymore. We have become rational creatures with a brain that processes and takes into account many different pieces of information before coming to a decision. I firmly believe that snakes are instinctual creatures.
Instincts are an involuntary response to a stimuli. The smell of a rodent triggers the instinctual feed response. A large heat signature and unknown scent triggers a defensive instinctual response, hissing and/or balling up.
On the outside looking in we as humans need to associate one of our rationals or emotions to a purely instinctual response. Humans feel the need to explain things, they cannot just accept them as they are. My two cents...