Some people have tremendous loathing and disgust of fat people. Why? We'll refer to this phenomenon as a phobia, similar to other phobias which manifest as loathing and disgust (as opposed to fear). Which people have the phobia and which don't? What causes it? Can people change to lose the phobia?
Meta: why does no one ask these questions? The issue came to the forefront in the censorship of a subreddit dedicated to mocking fat people.
Hypothesize it is because body shape is considered a marker of social class, and the phobia is a manifestation of fear of social class demotion or fear of failure at social class promotion. This hypothesis can be tested by measuring whether the phobia is correlated with other behaviors indicative of fear of social class demotion.
"A woman's greatest fear in dating is that the man will kill her. A man's greatest fear is that the woman will be fat." Whoever modified the original Margaret Atwood quote unintentionally had a stroke of genius. If the date is fat, then it means social mechanisms that he hoped or expected would insulate him from the lower classes, prevent the lower classes from accessing him in courtship, are not working. Those mechanisms not working signals the man may have suffered social class demotion. That his date is fat is a reflection of himself, or more properly, a reflection of where society believes he is socially ranked.
Incidentally, the original Atwood quote, that men fear that their date will laugh at them, is a manifestation of the same fear of social class demotion, fear of loss of respect associated with social class.
Both sides can reasonably fear that their date might kill them. But the fear of having to live with, being condemned to mate with, the lower classes is, for those who have this phobia, a fate worse than death. Compare it to an arachnophobe choosing between death or being surrounded by tarantulas for the rest of his or her life.
If this hypothesis is correct, that is, it is the underlying mechanism for hateful speech against fat people, then censorship isn't going to work because it does nothing to solve the underlying social class conflict.
The hypothesis can be generalized to other phobias regarding a person's appearance, most famously racism.
The meta question above is an interesting question, perhaps more interesting than the main one. There is a pattern of people avoiding difficult questions, but I do not have a coherent explanation why.