Can someone explain the joke?
The Romans were supposedly in the habit of executing prisoners with captured lions in their arenas. When Christianity was still a minor cult it was at one point technically treason to deny the Emperor was a god, and so being a Christian was technically a crime against the state by default. In these arena matches you'd throw some ill-equipped criminals against something they had no hope of beating and call it justice when they get mauled to death in the "trial by combat."
Anyways, the Christians with persecution complexes really like focusing on these few centuries of history with their millennias old church. This is a joke about both sets of prisoners signing up for the for "match" like it was a casual sporting event.
