@Captain:
You're misinterpreting my issue with Sanji. It's not that idolising women and treating like they're too fragile to fight is too sexist or outdated for me, it's that Sanji is a flat character and Oda has shown no interest in having him confront his most prominent flaw. And it is a flaw, it keeps holding him back and making him a liability to the crew. As I said above, it keeps getting used against him in important conflicts, and the only time the narrative has forced him to think on his feet and work around his hang ups was the fight with Bentham in Alabasta. Every other time he's lucked out by having someone else take over the fight or the woman who was playing him turned out to be good all along.
Now, One Piece isn't exactly known for its character arcs, but other members of the crew have noticeably grown throughout the story. Zoro's pride and "if you get between me and my dream i'll make you kys" attitude were flaws established in the opening chapters. He's since put Luffy's dream before his own and thrown his pride aside to train under Mihawk. He hasn't changed fundamentally as a character, but he has worked to improve the traits that might have made him a problem for his friends in the long run. Usopp learning to manage and push through his cowardice and insecurities was a character arc. He still has those traits, but he got the opportunity to work on them until they weren't holding him or the crew back like they used to. Nami has become much more willing to part with her money for the greater good. Robin has opened up and come to trust her friends to have her back. Even Luffy has grown as a leader and changed his conflict management based on his experiences through the years. But Sanji… aside from the non-flaw of sometimes being too kind, the biggest thing that's gotten in his way is his weakness for women, and not only has he not worked on it like other members of the crew, it's gotten more pronounced as time went on. And if the "Year of Sanji" arc with the female main villain and the honeypot plot wasn't the time to have him rethink how he balances his personal convictions and the good of the crew it's probably not going to happen.
I don't hate Sanji or anything. On my first readthrough, before it became apparent how permanent his issues were, he was among my favourite Strawhats. Now, it's just disappointing every time Oda chooses to confirm he's not going to grow or change or improve himself in the same way other prominent members of the crew have. I also don't need him to rush in and beat up every female villain; even just gaining the awareness that women can and will manipulate him, call out the femme fatale trying to do so and tagging out immediately for a more qualified member of the crew. (Because like there's a whole essay to be written on the delicate balance that should be struck between not treating women as too fragile to ever be in a real fight and creating things that might be taken as a positive depiction of or justification for domestic violence against women, which remains a big issue in a lot of societies. There's no obvious right answer, and the right answer is certainly not "just show more women being beaten up." It's a complicated topic!) But yeah, I'm not a hater or anything. I don't think characters have to be pure or even likeable people to be good characters, I just think Sanji has some wasted growth potential in this area.
Thanks for the well-articulated reply! Ok, I can agree with the angle that this character flaw of Sanji, as you call it, often endangers both his own as well as the crew's survival, and thus he needs to work and improve on it. I did indeed misunderstand where you are coming from and that your point of view was more because you felt Sanji's treatment of women needs to change because it didn't agree with your own moral values.
As others have already said, I think the 'problem' is that Oda simply considers standing by your strong principles, even if they may be dumb, dangerous, antiquated, etc., ultimately to be a respectable character trait. Someone aptly compared it to Ace just not being able to walk away from someone badmouthing Whitebeard, even if it meant his death. I think another good comparison is Bellamy keeping on fighting for Doflamingo even after he has discovered that Doffy couldn't care less about him and tried to have him be assassinated by Dellinger. If I remember correctly, all of these instances were met with annoyance and anger towards those characters here on Arlong Park, so apparently this trait of standing by your principles even if they are stupid and dangerous isn't admired or respected around here in general. I would be pretty interested how Japanese fans regard these flaws.
Anyway, I do think Sanji's other main character 'flaw', i.e. being too kind + his pride as a cook leading to him feeding enemies even if they will be a danger afterwards is very similar, yet I don't see anyone demanding that he'll abandon this flaw as well. You tried to handwave that by saying that, well, at least he can defend himself afterwards, but I don't think that is generally true. Him feeding Don Krieg and his crew back in the Baratie arc really would have screwed Sanji, Zeff and everybody else on the Baratie over if Luffy hadn't been there. Sanji is strong, but I think it was clear that back then, the cooks would have ultimately lost if it hadn't been for Luffy. So this flaw can absolutely have dire consequences for the people he cares about - yet should it be the right thing to do to just throw away your moral values if they might lead you into trouble? I just don't agree that this line of thinking is where character growth should lead us to - certainly not in One Piece. Sure we had Zoro throwing his pride away in order to help his Captain and crew, but I don't think this is inconsistent - Usopp similarly had to suck up his pride and apologize to Luffy Post-Enies Lobby, so Oda clearly does think that there's such a thing as misplaced, or maybe selfish pride. It should also be noted that pride and principles are not exactly the same. Zoro may be a prideful character, but it has never been established that bowing down to someone and asking for help goes against his strongest principles.
Similarly, Usopp overcoming his cowardice is also an unfair comparison. Being a coward has nothing to do with Usopps principles, after all - it's simply a personal weakness. I also remember that one of the big messages that Sanji himself imparted on Usopp in Enies Lobby, after losing to Kalifa and then saving him from Jabura, was that nobody needs to be able to do everything as long as you have friends who can help you out. While Usopp is also constantly growing stronger, him still being weaker than most of the other Strawhats and thus unable to beat the really strong enemies is nothing he should feel bad about - his stronger friends can do that for him while he can accomplish other things to help them in turn (as in that case, being such a great sniper that he could save Robin in time from miles away). Why can't it be the same for Sanji? He's clearly an asset to the crew in many other ways - why can't he preserve his personal principles while his friends take over to do the one thing he can't?