I too think the fashion look of "sagging" is a dumb look. My concern is having our government try to legislate it. If the law holds up as constitutional; and I think someone will challenge it and win, then what is to stop our government from outlawing sandals... or cowboy boots... or two piece bathing suits, etc..
They have already put a big dent in smoking, and No, I don't care. I don't smoke. But what if they outlaw chewing gum?
What is the old saying? "You can't legislate morality."