Stiglet, any even remotely rational person would realize that if you wrongly deploy the emergency slide while the plane is at an airport, the chances of getting caught and punished are 100%. It's obvious on the face that this was not even a remotely rational act; I can't imagine how you can call this person sane.
That doesn't, of course, excuse the behavior, nor relieve the perpetrator from responsibility for making the victim whole again, e.g., by paying for a new slide, etc.
But calling for draconian punishment, when it's already obvious that the threat of 100% certain and negative consequences did not deter this crazy person and will not deter future crazy people, isn't going to prevent this from happening again; it's only pointless retribution.
There's a difference between putting a criminal in a cage to punish him, and putting an intractably crazy person in a cage to physically prevent him from injuring others: In the former case we should make the cage experience unpleasant; in the latter case there's no reason not to make the cage experience as comfortable and pleasant as possible.