cutee_tigress already mentioned the reasons why no one is, 'cause it's not as much a problem as fat shaming.
Honestly, this is like pale people talking about how pale skin is criticised too on videos about dark skin . It's just belittling the real problems which the other group is facing. Diverting attention from real issues of discrimination.
Fat people face a lot of prejudice on the internet and are bullied, which leads to low self-esteem, depression and what not.
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