Freedom of expression and the right to freedom of speech. The right to hold certain beliefs. The right to express those beliefs. The rights of others. Respect for other people. Respect for other religions.
It's a fine balance. Sometimes people get it wrong. Some want it all their own way. Some feel they can criticise but want to be protected from criticism. Some wish to provoke without recourse to their actions, whilst reacting to any provocation, real or imagined.
We all remember the cartoons which upset followers of the Islam faith. If these caricatures upset, why do they then respond in the same fashion against the Pope? Which image upsets? Which offends?