this is idea is super boring. literally no body positive people are saying that skinny people are the devil. it's terrible that any body is policed for not being the ideal and no body represented in the media is realistic. but thin is what's held up as the standard of beauty for women. disparaging things said to skinny women is backlash on that basis, the only thing that came close to being good is the bit at the end where they all pat themselves on the back for not being fat because even in body positive circles, "you're not fat you're beautiful" is seen as a complement when those 2 things aren't mutually exclusive.
It's not really well-done, but the point I got out of it was "imagine if we shamed skinny people, the way fat people are shamed" - as a way to oppose fat-shaming.
I'm pretty sure it's supposed to be a rebuttal along the lines of the people who come out of the word work and say hey I get shamed too as a skinny person and then react badly when fat people say ok but you're still the accepted body type.