Justin Beiber is the king of dissing? Uh, no, Eminem is 1000000x better at dissing than him, really the only popular artist left that can diss with words properly, not money, same goes with his talent.
And you cant really compare him to when he was Justin's age because at that age he almost always had a black eye and bruises all over his face from when street muggers beat him up for money he never had :/, something Justin doesn't have.