Yeah it is incorrect to say that "Oda doesn't hurt [beautiful] female characters in One Piece" but the problem with the different gender treatments by Oda is there definitely is an imbalance.
With the Nami and Usopp VS Ulti and Page One, Nami was never going to be shown getting headbutted on panel in such a brutal manner. That's the reason Usopp, our god and savior of the One Piece world, was there.
When readers state 'Oda could do with hurting females characters more', I don't disagree with that. More balance is needed. I personally would like balanced battle focus to be given to ALL the Straw Hat Pirates save Luffy of course because main main character (*looks at Zoro - 'are you sure you not the captain?').
It has been 732 chapters since Robin got a proper battle (1 vs 1) to be featured in. Yeah there is the Hammond fight but that was only two pages =/. Robin was also the only Straw Hat Pirate during the climax of the Dressrosa Arc not to get a battle to feature in. Oda has been writing Robin as support for so long and it has become such a tragic tale for the fans. Robin is such a badass character with so much potential.
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Oda clearly has a preference to how he writes female characters and sadly sometimes it becomes vexing. Just look at Smoothie compared to her Sweet Commander counterparts. Can you imagine if she got the same treatment as Cracker and Katakuri? Or half of that treatment?
This is why in addition to Nami and Robin, I like characters like Monet, Yamato, Kuina, Miss Monday, and Zala (I'm sure there are one or two I'm forgetting) who have had focus beyond what Oda's usual writing style is for female characters, especially in battle. Such characters are also written to exist beyond their "femininity".
Considering how Oda has presented Black Maria - the most understanding member of the Tobiroppo with a nature leaning towards clemency and forbearance - and the stage at which the arc is at, I don't expect a battle between Black Maria and Sanji to ensue. Sanji is going to escape. And if Black Maria stands in his way, he is not going to engage. The only way I can see Sanji being forced to face Black Maria is if she has captured allies of the Straw Hat Pirates i.e. Bepo, Shachi and Penguin. It would be cool to see Sanji avoiding injuring Black Maria but succeed in saving those captured by her.