Madison police report a Chicago man was knocked out Saturday night when another man sucker-punched him.  The 26-year-old victim was walking with a female friend when the other man grabbed her backside.  When he told the aggressor his actions were unwarranted, he was hit so hard he went down, with his head bouncing off the concrete sidewalk, leaving him unconscious.  He was taken to a Madison hospital for treatment of facial injuries and broken teeth.  The man’s name hasn’t been released and his condition isn’t known.  The attacker was described as a black man with light complexion, about five-feet-eight, with a thin build.