Okay, my understanding was that you were arguing he wasn't going to participate in pointless violence that has no reason to exist like the giants.
Since you are, I refer you to my original comment on it, which kicked off this whole debate: The giants and now Usopp is a fucked up perspective on virtue and honor and it should be acknowledged as such.
Again, you're looking at another world through the lens of our own. You aren't taking that world as it's own thing. Stuff like this needs to be taken in context, you're taking it out of the context of the story and pretending it's in a completely different context. Part of understanding a piece of writing is being able to take it as it's own thing, you, as always, are going way too specific on a thing and lifting it out of it's original context and then complaining that it makes no sense.
No, not duels. I'm okay with duels as a concept. But this particular example is stupid in it's absurdity and disgusting in it's glorification by the character. It is a duel where the original point of the duel has been forgotten. A duel over which the original point, when revealed, was revealed to be trivial and an idiotic thing to start a fight over (who caught the bigger animal). Duels that last so long that they consume a third of men's lives. Duels where the people's lives aren't consumed ONLY by that duel and nothing else.
I have no issues with fighting for a principle or something, but lets be clear: the giants were not fighting over a principle. They just loved fighting. They worshipped fighting. It was an indulgence, and they abandoned the rest of their lives to do it. They loved it.
The concept of duels in general might reasonably be considered iffy, but this goes way, WAY beyond any other duel concept I've ever seen. And glorifying this particular iteration that is so utterly pointless that removes you from the world for the sake of the most petty perception of honor I've ever seen is what it is: fucked up.
And again, I'm fine with Usopp doing this as a character. I just wish the writing would acknowledge how disgusting it is.
So you're looking at it through your own morality, ignoring the original context, and complaining that it doesn't ascribe to your world view. I don't know what to tell you other than to take a class in critical theory.