They're the opposite of proud. They're ashamed. Shame is the root of all shitlording. That's why this young woman's comments induced such oinking from the ham: she hated to overhear the truth that fat people are fucking embarrassing and no one actually wants to be fat. Butterbarge can insist until it's blue in the face that it's a "proud fatty", but there is a point where no self-delusion can overcome the terrible shame of its girth.