A joke works because it unites two worlds, two perspectives, while showing them to be apart. A pastor/leader who can't tell a joke should not be , has not been, called. He doesn't have tone maturity, timing, who can't tell a joke.
A coarse joke I've been telling recently has caused people to whom I mention it again to burst out laughing on this re-mention. And one person came up to me days later and thanked me for it, and another, saying 'They've been bouncing around my head for two days'.