I was watching an episode of The Simpsons, Bart was playing basketball for Springfield and winning all games. Then Fat Tony bribes him to lose the game. When Bart loses and everybody finds out about the bribe, all the people get upset and it shows lots of messages of disapproval around the town. One of them caught my attention, on a billboard in front of the church the expression
Jesus saves, Bart shaves.
What does shaves mean in this context? Is it something offensive?