What exactly is the Poya-gun?
It's an electricity based self defense stun gun, comedically shaped like a retro style ray gun, likely of a not very high amperage as it doesn't seem to have much of a disabling factor on Gamon. People probably don't react because it's anime and nobody really cares that the 'main' is being abused by his friend. Of course, stun guns (tasers) don't actually work like the show implies the 'Poya Gun' does (as tasers don't have ranged ability, relying on you touching the arc to the victim for it to actually work.)