There is none. “
How about an assassin’s bullet? Francis is going to bring down the Catholic Church if he's allowed to "stay on!" They may as well have voted Obama in as Pope.
If you set the norm that it’s OK to murder popes you disagree with, (1) it martyrs people that should be discredited, (2) it’s not only people you dislike who are going to be murdered in a climate of escalating political violence.