Or a thin shamer,etc, to be honest. Anyone who insults anyone's body type.
"Don’t insult people’s appearance. It’s rude and tacky.”
“But I’m just saying . . .”
“Don’t insult people’s appearance. It’s rude and tacky. If you can’t agree to that basic rule, our conversation is over.”
That’s what you do. You have the right, as a parent, to set rules of discourse with your children, and one of them can and should be that it is no more acceptable to mock people for the shape of their skin than for the color of it. Mocking other people’s bodies is a nasty, childish, uncivilized habit that is beneath dignified people. It’s OK if this is something Mom is totally unreasonable about — OMG, it’s like you can’t say anything around her! They’ll thank you when they’re older.
Maintain similar rules in the rest of your life. There is no trash talk about bodies under your roof, at your table, or in a conversation you are participating in.
Period.
It’s that simple. It seems not so simple, because you’re heavier than you’d like to be, so you’re feeling guilty and embarrassed, as though perhaps gaining an extra 10 pounds lost you the right to demand courtesy — and because American anxieties about health and money and social class and gender are tied up in a great garlic knot of a complex around food and fat.
People who mock fat people are terrified of losing control of their temporarily acceptable lives. They fear dependency and loss of control, of being an object of pity instead of envy. To these human barracuda, being fat is the most visible symbol that you have “failed” at something — health, femininity, upward mobility. And they attack.
So don’t let them. Use the phrase above like a vampire-fighting priest would brandish his crucifix, and don’t back down. Do not under any circumstances let the subject get derailed to the obesity epidemic and Food, Inc. This isn’t about high-fructose corn syrup or Obama-care or any other damn thing a fat hater wants to derail you with. It’s about not making fun of other people’s bodies. This is so fundamentally basic a premise of etiquette that anyone caught violating it will usually come up with some elaborate excuse for why that wasn’t really what they were doing. You are not at home for these excuses, nor for any argument about how truly well meaning these comments are. (Fat haters are among the most shameless of trash talkers, with a capacity for self-serving logic that rivals that of the chemtrail crowd.) Keep repeating the phrase above.
If you’re interested in weight and social issues generally, I’d recommend Lessons From the Fat-o-Sphere by Kate Harding and Marianne Kirby. Don’t read these things with the intent of bolstering your ability to argue with your family, however. Because you’re not going to argue with them, you’re simply going to lay down the law."
See the question that triggered that response @ The Boston Globe