I think most of us wouldn't feel right with genuine fatphobia. Just fucking with people because they're fat regardless of what they're doing about it. The kind of stuff where a fat person goes to the gym and you keep sniggering about how they're gonna break the machine until they leave.
The difference is that people like Amberlynn use fatphobia as a way to deflect any and all criticism, which only makes people so mad they wanna poke at their weight as much as possible to break them on purpose. That's what a lot of "phobia" boils down to though, is driving people crazy by playing the victim until you actually become victimized and have something to bitch about.