It doesn't. The first amendment restrict government, not individuals.
That said, there's no exception to the laws on assault for "offensive speech" either.
But the guy was only charged with harassment, not assault. He should have been charged with assault. Since he admitted that he laid hands on the “Zombie Mo”, at least to the police. He was clearly the physical aggressor. yes the atheist was being deliberately disrespectful, but they other atheist was being disrespectful of the Pope, and no Italians jumped out to harass or assault him. , nor any German Catholics for that matter. (The Pope is German after all).