Fat acceptance my ass, enough about that let's talk about fat rejection.
Loving yourself is important, but self improvement is even more important, accepting deffects you can't change like your face or hair etc, does affect your confidence by a lot, but accepting the deffects you can actually change, like your weight, just lead to mediocrity, stagnation, and depression, if you can do something to always be the better version of yourself, you shall never stop doing it, i'm not saying you have to be buffed, but at least keep a decent bmi and weight to have a healthy and long life, because believe it or not, having a healthy life style makes you happier, and your emotions also determines how much are you gonna live, if you are happy, confident, and you improve yourself everyday, you won at life, that's my problem with fat acceptance, we already accept fat people, but is it wrong to want to promote a better lifestyle for others? I never tell others how live their life, but as a word of advice, mediocrity does not make happiness.
I used to weight 95 kg in highschool (i'm 1.87 mts (6'2 feets) which is basically, an slight overweight, still i felt a big complex about it, so i decided to make the change and i did managed to lost 20 kg in just one year, i was 75 kg and i felt in my prime, then i fell into depression and i got 10 kgs of extra weight, but now that i'm recovering i'm going to the good old habits, i need to rise back, in this month i already lost 2 kg, so i feel extremely satisfied and motivated by my progress and changes, i wish more peopl would see themselves like that, not only for aesthetics, but for their mental and physical health, as you say, fatphobia is not like homophobia or xenophobia that can get people killed, fatphobia is basicallytelling a fatso that they should excersise, that's all, never stop the grindset, always engage in self improvement.