Ex-UFC star Anthony "Rumble" Johnson is fighting back in his domestic violence case -- pleading not guilty to allegations he roughed up his girlfriend during a dispute earlier this month.
TMZ Sports broke the story ... the 35-year-old fighter was arrested in Palm Beach County, Florida on May 6th after his girlfriend told cops Johnson got physical with her during an argument.
According to the police report, Johnson told cops at the time he DID pick up the woman to carry her to another room because he was sick of arguing .