Does deterrence harm the bear?
So the bear won’t get ‘stuck’ to the fence from seized up muscles; instead, it will be released instantaneously to run away and think twice about approaching your or anyone else’s campsite again.
The outcome that lasts is not physical damage, then, but psychological deterrence.
Bear Sentries are actually “good” for bears, because zapping them modifies their behaviour: they learn to disassociate food from human spaces and avoid campsites and homes where they can end up in unfortunate conflicts with us (leading to what are called ‘defensive kills’, and more orphans sent to the Northern Lights Wildlife Shelter, if they’re lucky).
So when your Bear Sentry goes into action, it’s good for you and good for the bears.