paul nungesser was accused of raping former friend emma sulkowicz .
the case attracted international attention as she paraded her mattress everywhere she went in protest , calling for nungesser 's indictment .
a judge threw out the case which branded nungesser a ` serial rapist '
he is now suing the school for failing to protect him from backlash .
nungesser , who is german , says the school presented the claims as fact .