Cody Gibson

UFC fighter Dennis Bermudez tells TMZ Sports ... fellow UFC star Cody Gibson took the "smart approach" by not murdering the guy who punched him in a Vegas bar ... because if Cody would've punched back, he'd be in jail right now. Bermudez -- ranked #8 in UFC featherweights -- was out in NYC…

File Under: "You Know You're In Trouble When" ... you punch a guy in the face as hard as you can -- AND HE DOESN'T GO DOWN ... because the guy you punched is a UFC fighter. That's exactly what happened in Vegas -- when 27-year-old UFC star Cody "The Renegade" Gibson (12-5) got into a standoff with…