Apple made store computers available for demo, installing spyware on them clearly violates the level and kind of authorisation apple was providing. THe law makes these distinctions.
But likewise, so does anyone with half a brain. You cannot come into my house an d install a keylogger on my PC, even if I make it available to you to play around with for other reasons.
Apple makes the computers available for the purposes of demonstration. No rational person would ever think this includes installing spyware on them, so you are exceeding the level of authorization Apple gave you. I strongly believe a court would see it the same way.
Excess is a very broad condition, and deliberately so. The law doesnt say what counts as auth one way or another, that's up to the courts to interpret.
It seems beyond doubt that any reasonable court would find this guy did not have auth to install anything, let alone spyware.
Anybody can install spyware on a public computer, anybody can install spyware when given permission by the property owner. Installing spyware on a public computer (that you do not own) without permission of the owner is very much illegal.
Unauthorised entry is unauthorised regardless of whether you have to open a door or break a lock. Not having to circumvent protection measures does not make something legal.