Oh come on, in every aspect of life somethings look good and other's don't. I would never tell anyone what to wear, they are free to wear what they like, but I do not have to like them in it or think it suits them.
All of us at sometime in our lives come to terms with the irregularities of our figures, none of us is perfect. I have no waist, my hips are where most people have a waist and I have learnt from the bitter experience of photographs, that anything that belts around the waist, makes me look like a sack of potaoes tied in the middle and 5 sizes bigger than I actually am.. This applies whether I am overweight, weigh just right or are under weight, while clothes with a high waist or no waist at all are more flattering.
As a general rule if you are plump, it is best to avoid clothes that cling. If you do wear them, you have to accept that others will think you foolish.
It has got nothing to do with women supporting each other of getting into groups and fighting. It is a simple aesthetic judgement.