As a fat dude, the fatphobia craze has devolved as an excuse to never take responsibility for your physical health. Losing fat takes a lot of physical and mental work. Take into account different metabolisms and people just thinking freedom and liberty equals not changing their behaviors and you have a fat epidemic.
Ive tried to lose my weight over the years with exercise and have gone down 100lbs and still have ways to go. In that time ive been ridiculed for exercising or just being by myself in a public space. Being an asshole to fat people will just make them eat more to fill their black hole stomachs and calm down the anxiety. Being fat is an addiction unless you have some medical reason. You dont know that person and if you have to need to make fun of it, then congrats, youre trying to feel good so you can forget about your own insecurities and shitty traits for a second.
Do be an asshole to those fat fucks that say going to the gym is phobic in some way, that being weak is ok or that that being 400lbs is healthy.