Overweight, heavyset, pudgy, plump, obese, big, well-nourished—these words exist and are used as euphemisms.

I am not sure that historically fat when applied to people has ever been value-neutral (though it should be) In the ancient Mediterranean fat was good because it meant you were a rich noble heroic aristocrat who could afford plenty of food. Now it means the opposite in class and economic terms, reenforcing stereotypes. It doesn’t take an abuser to say it to make it bad.

I think also fat has more rhetorical and aural impact as an English word because it has a lot of the same characteristics our more popular curse words do: monosyllabic, short vowel, ends with a plosive consonant. Its sound is memorable.