If there was one lady mean and threatening enough to make Sanji consider it, it’s Big Mom. But even I’m not sure how it would play out.

I don't think so because Sanji doesn't break oaths.

Big mom looks like a man

He kind of already did

It was to protect Reiju though

Well, I would say he would attack but as a way of defending and not an actual attack. It's more of defending instead of harm.

The misogynist paradox