Well - I can only say that it does seem a significant issue to me, in the same way that racist and sexist language matters.

Nothing wrong with saying in a neutral way that someone is fat, or a woman, or black, or whatever. But unfair negative labels easily get attached to groups of people - often things to do with being lazy, or stupid, or ignorant about health, in the case of fat people. I think that comments that link fatness to undesirable behaviour that has nothing to do with body shape reinforces these negative labels unneccesarily.