You're being way more lenient with what is intepretted than is warranted in this series. You're basically saying "No, of course he wouldn't do that, that'd be ridiculous".
Well...yeah. That's One Piece for you. Who the hell in this series isn't ridiculous? Luffy eats giant pounds of food, Chopper just a few chapters ago couldn't stop munching on Pudding's cafe, Usopp makes the most exaggerated lies, etc. You can call them gags, but that doesn't stop them from being actual things that happen. These are acknowledge events, other characters witness them and interpret them as literal truths. That argument really goes around pretty often as a way of dismissing a lot of the stuff that happens in the series that doesn't make sense in some level, and whenever it's brought up, I always think "What do you think is actually going on that gives us a consistently distorted view to the point where the reader can't be trusted to view repeatedly acknowledged events as true?"
So yeah. I totally think that Sanji is the kind of dickhole who harasses people into finishing food they don't want. Why wouldn't he be? Every instance we've been shown of people not finishing their food has shown him to be exactly that. To deny this, your argument would have to come down to convincing me that what I see happening consistently across the pages of the manga on multiple occasions is just some kind of fever dream exaggeration of reality instead of what is actually happening. In the face of the fact that hundreds of ridiculous things do actually happen in OP, why wouldn't this also happen?
Why? Sanji has no issue calling out and starting fights over anything with the male strawhats. They'd probably just avoid this issue by Sanji making right proportions and the crew finding his food too delicious to stop eating until it's all gone.
So yeah, I totally believe that they either always eat until there's nothing more or else Sanji starts shit over there being leftovers. Again, why wouldn't I? Because that's ridiculous? Welcome to One Piece. That's the thing when you go this extreme with silliness, it doesn't stop when such issues pop up. Because that'd make Sanji a dick? Well, yeah, that's my point. That's been my perception of him since he was introduced.
Honestly, worst case scenerio, if someone else REALLY doesn't want to eat more and Sanji can't force it down their throats (despite trying), he'd just eat it himself so as to not waste it, but he'll be pissed and mutter about the crew in resentment over it. But if you're still not convinced, just think about this: when have we ever seen a character drop a characteristic they believed to be important? One of the most recurring themes is that if find a character has some idea, they NEVER stop enforcing it. Whether it's Luffy never giving up a fight or shit like that whale waiting for Brook's crew for decades on end and brook still someone being obsessed about the stupid thing to see it again, or Whitebeard and his entire crew, we have literally hundreds of examples that when characters say "I value this", then they go to positively psychotic lengths to enforce it. Sometimes, it gets to the points where it's just incomprehensible, like how Bellamy STILL believes in Doflamingo, even after he's repeatedly betrayed, shown to be a horrible person whose values don't line up with Bellamy's, and even made friends with Strawhat, his mortal enemy...but he is still loyal to him at heart. That's not even the first time that's happened, back with Gin and Don Creeg or whatever, Gin took him back to safety after he repeatedly demonstrated no value for him. All because one commonly recurring value for men in general is that they stick to their captains, even when they hate them.
So, with all that acknowledged, you're telling me it's unlikely that Sanji, after getting extensive explanation for why he would never waste food, and being shown to enforce this belief over hundreds of chapters, every time it was brought up, is going to drop it whenever he's off panel? Because I'm supposed to believe that Sanji wouldn't go out of his way to make sure there are never any leftovers? That it'd be too rude, even though rudeness to men is one of his defining traits? Nu-uh. Not in this manga.
Thanks, and I don't mean to offend you either. It's just that, from the above quotes I made, I feel you're skewing Sanji into a more likable character than he's actually been depicted as. He HAS given people grief over not finishing meals, even strangers and people whose decisions he has no right to encroach on, and we've never been given a reason that he's ever stopped. The only arguments I see is that it would be unrealistic for there to never be leftovers from Sanji's meals (which is a self defeating argument when the event takes place in one of the most unrealistic manga I've ever read) and that Sanji would be a bit of a dick if he did that to people (which....yeah, he is basically what I'm saying. He's a dick.)
Now, it isn't to say that he hasn't done good deeds through the manga, or that Niji acted in an acceptable manner, or that Sanji wasn't even on edge because Niji was needling him and so on. All that's true and all. But it doesn't change Lunar's argument that this was about ideals, the things integral to his character. And the ideals that Sanji espouses are things I find distasteful, atleast how he frames them, if not in principle. So when Niji acts like a dick for no rational reason, it feels more like the manga is trying to pigeonhole me into supporting Sanji's view just because his opposition is worse than him, and yeah, I resent that.
Fair enough. Like I said, I acknowledge this feeling is very subjective. It either matters or it doesn't. I find it an interesting topic to talk about because storytellers can't help but try and skew things a certain way, so it's kind of fascinating to me to think about how it works that sometimes I can be offended by it, sometimes I never even see it, or sometimes I do see it and just tip my had at a moment well manipulated. It's one of the least explicable elements of storytelling, because it's simultaneously supposed to be invisible, yet everyone knows it's there. It makes it difficult to parse when it works, when it doesn't, and why.
