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As psychology student, I WAS AND AM AND WILL BE HAVING A FIELD DAY WITHW THIS BOY.
We all know that Zeff was the one to drill into Sanji's head that he is to under no circumstance ever strike a woman, but he wasn't the one who taught him to fawn over every lady in existence. If anything Zeff tried to kick that out of him. I like to think that actually came from Sora. I think watching his mother get abused and treated so horribly forever changed the way he interacted with the opposite gender. Maybe she use to make Sanji promise he'd never be like Judge. He'd treat his own future princess like the kind & honorable prince in the picture books they read together. To always treat her like a precious gift.
So Sanji being Sanji takes it a step further & decides to treat every woman he comes across like she could be his future princess. Even subconsciously, I feel he would hate to think of any woman being in the same situation as his mother. So when he's flirting with a customer on a date at the Baratie it's not just about him being a flirt. He wants to make sure that if this lady is in a situation where the man she allows in her company is being an ass she has another frame of reference to compare them with. That way if she's ever getting yelled at or hurt she can think of the random waiter who didn't even know her, but was able to treat her with more love & care than the man she's been living with for years. To remind herself that there are better options out there. That she doesn't need to settle.
Maybe that's why he over reacts to any perceived slight against a lady because how dare you. He knows the power words hold and the very real pain a man can cause so in an attempt to protect he overreacts & becomes an issue himself. Somewhere along the way he confused his respect with lust & his need to protect with possessiveness. This is something he needs to learn to undo himself. Hopefully by the end of the series he's done enough internal work to sort this out & come out with the healthiest version of chivalry he can.
So he may not always react the way he should, but the intent is there. He's never going to stop either so don't even try. Because whenever he sees a lady in a vulnerable position maybe just maybe it's his mother's face looking back at him. And he's not powerless anymore. This time he can do something to help. To stop it.