How do you handle being around rude family during the Holidays

My family, specifically my mother is so opinionated and rude and just doesn't care. She's 75 so she's probably just stuck in her ways but July she kept making comments on how much my son(14) was eating. He had went to get a third piece of lasagna and she said "Wow. Someone is a little piggy." And I told my mom that's not nice. She said "He's getting pretty chubby. I hope he loses all that before Christmas. I want good pictures for that ugly sweater contest. " And before anyone starts, my son is chubby but not unhealthy. His doctors are not concerned at all. He also has muscle from playing hockey. She kept making these comments and calling him a piggy. When my Dad cut the watermelon and my son went to get a piece and made comments again. I don't know what she said that time. Just know my son yeller "So I can't even fucking eat fruit!' and went to the car. My husband came and asked why our son was crying in the car and my mom said "This generation of boys are so sensitive." We have thanksgiving at my mom's house and even though that's months away, it came up and my son said he will make sure to eat a singular grape to keep her off his back. How do you deal with rude family that are stuck in their ways. My son also lost his dad less than a year ago so I know he's extra sensitive and want to be prepared.