TMZ is reporting that Bieber was actually knocked down by an undercover cop who had lept to his defense when a crowd got rowdy; not realizing he was a police officer, Bieber got defensive, and his security team tried to pull the police officer away. Things were cleared up, however, and disorderly conduct charges against one of his bodyguards were dropped. Scroll down for a photo, and click over to COED Magazine for more. Justin Bieber was jumped and knocked down by a man outside a New York City...