He would surely know that bongs and pipes and hookahs *might* be used as drug paraphernalia -- unless he has been living under a rock all his life. That hardly makes him a "true innocent" -- tho' it might make him "technically-not-guilty", which isn't quite the same thing.
By selling that stuff he is skating about as close to the edge of the ice as is humanly possible, knowing full well that he's so close to breaking the law it's not even funny. That's why he gave the guy $40 bucks: he knew he'd be in for a hassle if the police came to his store.
If he was a true innocent he would have held the perp at gunpoint and waited for the cops. However, he had the conscience of a guilty man, as his actions proved. Actus non facit reum nisi mens sit rea.