If we lived in a society where scrutiny and vitriol were pointed only at the ruling class, we’d live in a utopia, but we do not and therefore should not. As society sits, making fun of someone’s physical appearance or disability yields the ultimate conclusion that everyone should feel, for these characteristics, innately lesser, and that’s not cool.
For instance, and to be topical, would you feel comfortable hearing someone refer to Neil Gaiman as a twiggy, autistic rapist? Because I wouldn’t. No need to associate weight and processing difficulties with the propensity and desire to hurt other.