[Yumi(e)]

Maybe because overweight people already have enough of that around to tease, and now her/his favorite artist do the same (or he/she felt as if)
It is a delicate issue, because a Japanese or Spanish will not get a disease because their country is represented in an absurd or wrong way (chinese jokes for japanese, olé and sevillanas for spanish); however an overweight and low self-esteem can develop an eating disorder.
But of course, they are "fat weeabos" so whatever.