At first I was thinking "I don't get it - I don't speak French." then once it showed the car it all made sense.
Sort of reminds me of the Twilight scene where the tourists are all led into the Vampire's Chamber to be eaten and all you hear when the doors close are the screams.

Honestly I barley understand French and have no idea what they are actually saying but this joke seems to explain itself.

Oh by the way if no one has noticed the guys in the pink the guards if you say look familiar because they are modeled after Sylvester Stalone and you can see them guarding the president in several different clips from the show.

The joke is actually the reverse of what you would expect if you don't speak French. The two cardinals and the Pope are walking to mass. The Pope asks why they cannot take the Popemobile to get to Church. The cardinal explains that they needed the Popemobile to protect the choirboys on the road to the Church. He then asks the Pope whether he would reconsider the Church's position on allowing priests to wed. In short, the Pope and the cardinals did not kidnap the children, but are rather using the Popemobile to protect them from out-of-control priests.

Actually thats exactly how I figured the conversation went mainly because the cardinals and the pope are on the opposite side of the rode.