I imagine the idea is to defuse the tension, which is a good idea in itself. I think there are better ways of doing it.

Joking in the face of death and hardship can be a good way of coping with it better, for people who are themselves caught up in it anyway. I'm sure there are a fair number of jokes among the people in the Church of the Nativity. But I can't see it as quite so appropriate for lookers on.