Herb Dean's one of the more respected refs in MMA -- but UFC fighter Sabah Homasi says he F'd up BAD during his UFC 218 scrap ... and there should be hell to pay for his actions.
"He knows he f***ed up," Sabah told TMZ Sports, "His facial expression was like, 'Oh, sh*t.'"
FYI, Homasi and Abdul Razak Alhassan were trading BOMBS in round 1 ... and Herb jumped in when he thought Sabah was out of it.
It reality, he wasn't even hurt ... and The Punisher ain't gonna let Dean off the hook, especially since he potentially screwed him outta some serious cash .