So, it's sexist because the manga is framed that way, but when there's exceptions, they don't count. Your argument doesn't make any sense. What you're saying is that you want a super powerful female character. I can see a bit of a gender gap, there, but you're playing it up so that this male/female disparity in Zoro-strength powerhouses represents sexism as a whole. It's more like an authorial flaw on Oda's part. The argument that women are well represented elsewhere DOES mean something. Your argument is much more specific and is claiming to be broader than it actually is. An apple tree missing a few apples is still an apple tree. Suggesting that Nami being good at whatever is counterevidence of the sexism of OP's world. Does it destroy the argument against sexism fully? No... but it's not being wholly sexist at the same time, either. Everyone has pretty much agreed with you that there are problems, but you seem intent on showing us that these are HUGE problems that REALLY MATTER no matter WHAT exceptions there are. Nobody disagreed with you in the first place, man. We all know OP could portray women better, but our arguments still hold weight.
I feel we might have lost the forest through the trees in the minutae in the arguments, so I'll reclarify.
I am talking about the portrayal of power and strength within the series in the group dynamic sense. Even if you can find exceptions, the issue I am addressing is that this is a
rule in the first place. It's not that they don't count, it's that they are exceptions at all.
But I do accept exceptions as exceptions. I just don't count Nami as one. I mean, it
is good that she isn't just window decoration for fanservice and contributes to the group, but she's not a strong character within the context of how men are portrayed, which is the umbrage I am talking with the series. I am not even talking about Zoro levels of strength. Forget about that. Lets take a character more in Nami's weight class and look to how they're portrayed: Usopp and Chopper are often portrayed as being some of the weaker members as well, with Usopp flat out pointed out to be the weakest member of the OP crew. But when it comes to fights, he actually gets into physical confrontations and is portrayed in fights to a similar manner as that of Zoro, in being a warrior. Chopper can't fight on his own, but he takes rumble candy to get take different forms. Usopp has to use his wits to win, but fights.
Despite Usopp's weakness and Chopper's primary role to serve as a doctor, they're physically strong characters who participate in fights. They are still portrayed like pretty much any other male character in the series. They get in fights, they rek, they get rekt, they muscle out, they survive, they sometimes lose, sometimes win. They fight. In this sense, I feel that Nami and Robin have no excuse to be in the background as frequently as they are. Nami is good as a navigator, but there's no reason she shouldn't be a warrior as well. She has her weather abilities, and she can probably get creative with that. But for some reason this doesn't happen. Nor with Robin, who is an assassin with experience fighting and a powerful DF. This doesn't happen with most females, even if they are supposed to be strong according to the text. If they fight, it's usually against mooks, or else they get their ass kicked, and they're certainly never in a prolonged or brutal fight. There's always some excuse or another why they can't or won't compete in the same way. So, no, Nami isn't an exception to what I am talking about at all, because that she can navigate has absolutely nothing to do with my argument I am pushing. It was never "OP portrays women as useless", but "powerless".
If there is an true exception so far, Big Mom might be an it, since she is a Yonko and ought to step up and fight straight up, but we haven't seen that happen yet. I hope I've clarified the issue. I don't want a zoro level strong female character. I want a bunch of Zoro level strong female characters, a bunch of Usopp level characters, and everything above and below and inbetween. The women should be as varied as men. And I want them to get involved in the same way guys do. This sexism thing isn't about any one character, but the group as a whole.
So you want them to look feminine, but strong, but not manly strong? What do you even want?
I did say I was on the fence about her, did I not? And I am merely commenting on how monster women are treated as being more okay to hit more in combat with men. Alvida, for example, was punched in the face when she was fat and ugly, but untouched when she became pretty. I don't even know how you got me saying I didn't want her to be 'manly strong', as I didn't imply anything of the sort. I was just saying that by this paradigm, the loss of feminine features in character design seem to signify strength and are okay to hit. If OP became a series where you can hit women, but only if they're ugly, that'd be a problem too. I'm just saying that monsterous looking women shouldn't be the only ones who are alright to hit. If Big Mom is indeed an exception to the rule of OP being a man's world, that's good, but she shouldn't be because she's unfeminine enough to be onlimits to hitting. She should be an exception just because she's a powerful female character, nothing more.
Edit: One more thing, I'd like to address your argument in a general way. You are saying because Nami has uses to the crew, that is a mark against the sexism of the story, but I wouldn't say that's true. Look at the past typical sexist cultural norms, you will find that few of them ever considered women useless. People who told them to stay in the kitchen would say their use is in making food. People who told them they're only good for secretarial jobs would say they're use is bringing coffee. They're useful in bed, in child rearing, in cleaning the house, etc. Sexism was never about claiming women have no use but about denying them roles that culture deems unacceptable for women to have. At best, you can argue them having use is proof of a lack of misogyny on oda's part, which is slightly different. What an argument against sexism in OP might be is 1. Oda doesn't have a stereotypical 'role' that women like the way Naruto has them being medic nins (though one could argue they're largely meant for fanservice roles, but that's unofficial). Nami being a navigator doesn't mean being a navigator is a feminine role, for example, Robin being a historian isn't indicative of it being a gender role, etc. and 2. Oda has given her and robin and other female characters roughly equal characterization to male characters. That's what indicates to me that, if Oda is sexist, he atleast is more careful to characterize women than, say, Kishimoto, who he defined not just in societal roles but also in personality. So I have and continue to accept that OP does make some strides regarding it, I just disagree with this specific argument that you and apparently your cheer leader have proposed.
Now, if there isn't any more confusion, I wish to retire this argument. I've made my point as clearly as I can and everyone seems to be in agreement with atleast the broad strokes. If you have more questions, I'll answer them, but having gone on about this for essentially an entire page, any more I think just clogs up the thread. At this point, I feel it's better to return to your regularly scheduled broadcast.