Fashion
It is an age thing. Anyone who cannot abide any particular fashion is simply resentful deep-down that they are too old to wear the garment which is offending them the most, whether they believe it or not. They also forget what they were wearing at that age and what older folks were saying about them. They also forget that they did care a hoot what people thought either.
No one likes to be reminded they are getting old. It worries people that they will become bitter and spiteful if they get older. This is not a new phenomenon by any stretch of the imagination and is of course perfectly understandable. But we are young only for a short time, and certainly will be a long time dead. Let the young people be and free to enjoy their precious few years of youth.
