These aren't really GOOD reasons, but Paul Gerard is such a "smarmy" character that that could make people hate him as much as the actual murder would.
Also the fact that he's French could be enough to make a viewer funny about him! What I mean is, I don't know about other countries, but Americans are always given such a cartoony image of the French.
Again, those aren't good reasons, but they could work on viewers a little bit.