The whole saggin' issue is so much more than butts and everyone is going to have a different opinion - so I'll jump right in with mine.
For me, first and foremost is an issue of self-respect and respect for the sensibilities of others. Yes, it's a fashion trend and it'll end just like all other fashion trends - I get that. But in the meanwhile, I personally think it's vulgar and stupid to want to show your undergarments and have your butt hanging out of what is commonly accepted as outerwear. I don't want to see male butts or female butts. We used to make jokes about appliance repairmen and their butts cracks hanging out being gross - so why isn't it still gross today?
I get the fact, too, that young people are making a statement and enjoy the shock effect it has on people who aren't of their generation. Get in line - each generation has had something they embraced as daring and rebellious - most of us just didn't show our backsides. My personal fashion guideline is less is more - a teasing peek is far more interesting than letting it all hang out. And there's a time and place for various kinds of dress - or at least there once was.
One of the posters here asked who's right it was to decide what people wear ... well, it's the right of businesses of all kinds, schools, churchs - most kinds of institutions we must interact with on a daily basis - it's called a dress code, and it's perfectly legal and appropriate that if individuals don't have the common sense to know what one should wear in a given situation - those governing the venue, event or place of business do.
Sometimes it's a matter of being age-appropriate; sometimes it's a matter of safety; sometimes it's a matter of common sense and sometimes it's a matter of self-respect. I'm not a prude, but even shake my head in disbelief at the lack of good judgement people use when selecting their wardrobe. Simply put - there are few public venues where others want to see boobs and butts exposed. Personally - when a woman shows too much, I know I'm alone in thinking she has no self-respect and is sending a signal that she's just an easy tart. When males wear shirts open down to their navels or pants below their butt cheeks, particularly if their past the age of 21 - I wonder what shortcoming they're overcompensating for.
Personally - I think this "fashion trend" is just another sad indication of how little self-respect our young people have for themselves, and how little concern and respect they have for others - particularly young children and their elders.
I like the solution my son's middle school resource officer had for saggers ... he carried a big roll of duct tape with him and when he saw a sagger - he taped their pants up - both around the waist and making suspenders out of the tape. The child had to leave the tape in place for the school day and if they did not, they were suspended.
Sag if you must, but do it away from schools, churches and public places where you know others' will be offended. And know that I'm not alone in thinking you're a flaggin idiot.