I think the FA movement also uses more direct words to express ideas that apply to all -isms. The unqualified acceptance of the self isn't danced around - or so it seems to me, having first met the concept via Kate Harding. In fact, I am using my familiarity with the ideas of FA, now, to come to a form of mental/emotional self-love via therapy. Being able to love oneself no matter what is a central, CENTRAL concept in FA, and it's one that strikes close to home and makes me want to write essays that are beyond my actual writing skill.
I think there's a fair bit of truth to that. Fat-hate is the denial of rights and dignity based on moral judgments of perceived behaviours. To accept fat is to accept that fat people deserve more than the right to diet
, or to alter one's behaviours. FA cannot succeed if it imposes any judgments - to ask, "Who is healthy enough
to deserve dignity?" would be its anathema.
Any other -ism is, similarly, the denial of rights based on perceived behaviour that carries a perceived moral value. Thus, any other social justice movement has to refute both of those perceptions to justify why the class in question deserves rights. It would be preposterous for an anti-racist to suggest that speaking Black English is grounds for discrimination. But feminism, and particularly its earlier iterations, have struggled with this. A fair few strains of pseudo-feminist thought seem to suggest that women deserve rights only if they act like men.
Addendum: The reason I think FA distills these concepts is that weight is viewed as a changeable thing. Some of the rationale for eliminating other -isms is that the oppressed class can't change themselves into the ruling class, but that notion allows for the ruling class to still seem desirable. The general population does not see this argument as applying to fat-hate. Thus, the message of fat acceptance cannot simply be, "Stop hating fat people," but must be, "Start loving them."