WHEN will young Hollywood learn their manners? At the Stand Up 2 Cancer event held at Kitson in LA on Wednesday, co-hosts Hilary Duff and Mandy Moore (left) both demanded to “exit the rear en trance of the store,” according to one snitch. After their hosting duties, they wanted to sneak out to avoid any paparazzi, and “onlookers were shocked and appalled that they would try to leave early,” our spy said. Too bad for them, as they soon realized, Kitson doesn’t have a back entrance and they were forced to walk out the reg ular peo ple’s en trance.