Cloverjo - //When I see a man/boy with his trousers hanging down like that I find it very difficult to resist going up to him and hoiking them up.
Like Miranda in her sitcom. //
You need to be sure that you differentiate between fashion and necessity - the low-slung jeans worn by teenagers and your men are a fashion statement. It originated in the U.S. where young black men started wearing their jeans on their hips as imitation of prisoners who are unable to enjoy access to belts or braces, and as such, their trousers hang around their hips.
That should not be confused with gentlemen of a certain age who have consumed an excess of beer and / or pies, and are unable to fasten their trousers across their waists as design intended, so are forced to go with the 'overhang' look which is so singularly unattractive.