Character Analysis
Okay, first we have to ask, is he really a Frenchman? They're in England, they speak English, he points to his own "outrageous accent," and they even speak to one another in English. In the scene where they're going to get the Trojan bunny, they have to translate the French into English to understand it.
So maybe they're actually Englishmen pretending to be Frenchmen so they can be uncharacteristically rude? All this isn't just a shot taken at the French (a favorite British pastime)—it's actually a parody of the jokes that the British make about the French. Wheels within wheels, bro.
Everything is hyperbolic: the accent, the insults, the silly mustache and ridiculous-looking helmet and gauntlets, even the flippant way he conducts himself, holding his hands on the wall and slapping his helmet. Having the French be the antagonists in the film is more of a joke about a joke. So when the Frenchman says, "I shall taunt you a second time," we not only get some hilarious potty humor, but also some commentary about stereotypes… by using these stereotypes and taking them over-the-top.
Way to be meta, Monty Python.