My teenage son has a friend who wears his pants sagging so that his underwear show his mother goes along with?

it and says its style. I on the other hand will not allow my son to leave the house with his clothes hanging off I feel that this looks very tacky and Ive heard and read about several bad beginings of this so called style. I want my son to be neat at all times now I ask you am I totally way out in left field? Should I go along with this so called style or continue to insist that he looks neat?