HANOI (AFP) – Tran Huy Hoang stares in shock at the images of four Vietnamese teenagers slapping and kicking a girl whose hands try to shield the blows. "How could schoolgirls act so much like gangsters?" asks Hoang, the father of a 14-year-old girl, as he watches the video clip -- apparently filmed by another teenager -- posted on the YouTube website. The girls pulled off their victim's T-shirt and bra, leaving her half-naked. It was one of several clips showing violence among Vietnamese youth that have circulated on the Internet over the past year, sparking concern about the media's...