The pull up your pants mantra is respectability politics. Respectability politics might mean well but it has limits to it. Its not really a new idea. A lot of the ideas formed after slavery when organizers and thinkers were trying to figure out how blacks could move forward and be successful. Obama is the epitome of it and tends to mention in his speeches to black audiences. Sagging and Baggy clothes have a long history of being criminalized because poor people of color wore them and people didn't see it as proper attire. The only reason people really wore them is because many could not afford tailors or new clothes so poor kids just made them trendy. It goes all way back to the 1930's zuit suits now we call them Steve Harvey suits lol.