I like that when a conversation about 'fat shaming' comes up, half the debate turns into whether or not it's okay to be fat. As though that's the point.
I think you'll find the real point is that nobody's got the right to mock anyone else for any reason. I mean, sure, mock various things in general, I'm all for that, but when you start specifically harassing people over it, you just become a ****. Though, if you're going out of your way to take the piss out of strangers, you were probably already one.
Though this does remind me - there's that whole thing where implying somebody is overweight is an insult, even if it's not particularly damaging to their health. I have a friend who's rather large and kind of hovers in the middle of corridors, and took minor offence when I said "Dude, shift, you're taking up the whole corridor." Because, y'know, he occupies more physical space than most. That's not an insult, that's just reality. It was best exemplified, though, and I mean beautifully done, when a former co-worker posted on Facebook that an old college mate of hers had implied she'd gained weight since college.
She had. That's not up for debate. It was true. But all of her friends left incensed comments on her status reading things like "You're not fat, you're beautiful!" or "That's not a true friend, a true friend would never say something like that." Thing is, though, there's no way this girl is completely oblivious to her weight. Nobody is. So why would a true friend try to establish a setting for 'beautiful' and discount 'fat' from it when the person she's talking to is a bit fat? It's total nonsense to me. Complete and utter bollocks.