The power-trip of being able to impact Rekietas life negatively.
He envys Rekieta because he has experienced how its like to be socially succesful.
Rekieta also seems to be free from feeling shame or embarassment over what people online thinks of him and that is new for Josh, Josh is used to lolcows who crumble inside over online judgement, Josh is used to shitposters who compete to appear the most based in the eyes of the crowd, and Josh himself spends a lot of energy on how he is perceived by his community and releated communities.
He tries very hard to appear tough and smart instead of just not giving a fuck and being himself.  Instead of either saying "yes, i know i should loose some weight, its just hard" or just ignoring people, he feels the need to engage in elaborate reasoning to explain and defend why his course of action is actually based. He is deeply concerned with what the crowd thinks, even on an issue so far removed from politics/KF-politics etc.
Rekieta does certainly act childish, explain away things and try to appear "above it all" but that is his personality, its not because he is so deeply invested in whatever resentful shitposters on the internet has to say.
Even if people wont like it he will post that balldo review because he wants to, Josh could never be so free from the fear of judgement.