People didn't think Mr. Clean was the brightest light in the hall. He was stating the obvious by bringing up people's suspicions about the cheater, which wasn't going to be a popular move, right or wrong. It was something nobody wanted done.
Cheating comes in many form emotional and physical, emotional does include jerking off or masturbaiting to other people because you’re acting on your attraction which, being in a relationship means you are no longer allowed to do unless you’re with that person.