The Wisconsin jury determined that Diamond did not recklessly endanger safety, but he carried a concealed weapon and behaved in a disorderly manner.
The altercation occurred at the Grand Avenue Saloon in Port Washington.
Diamond and his girlfriend, Amanda Schutz were inside the bar when a group of intoxicated people started behaving in a rude and insulting manner, leading him to believe "there was going to be a brawl," he said, according to the arrest report at the time.
He said he turned to close his account and get their coats, but when he looked back, his girlfriend was bleeding and two men were holding her hair, the report said.
Diamond said he moved toward his girlfriend when a man grabbed him, the report said. Diamond said he might have stabbed the man with a pen used to sign a credit card receipt but later conceded he was armed with the knife, the report said.