User blog comment:12th Supernova/Chapter 851: Full Candy Jacket/@comment-53507-20161229233010/@comment-5398287-20161230022354

The difference here being that unlike with Nami and Robin, Sanji hasn't had the crew prove their devotion to helping and protecting him, and he doesn't need to - they've already reinforced their bond with him many times over. In this case, he's realizing that he's been lured into a completely shitty situation with neither side being one he can support after having already beaten the shit out of Luffy and acted like he was totally in line with his family just to protect them and Zeff, an act which in itself drove him to tears. Right now, unlike Nami and Robin, he feels absolutely hopeless and helpless because he doesn't know about Jinbe coming along to provide assistance. So you're right, it's different, but I think Oda really is trying as much as he did with Nami and Robin to make this feel unique to Sanji and like something that actually matters, and he's succeeding.