The Fourth Official

Buffer: something or someone that helps protect from harm
”The fourth official acts as a buffer for the referee.”

Lenient: not as severe or strong in punishment or judgment as would be expected
”The referee was lenient towards Jurgen Klopp.”

Berate: to criticize or speak in an angry manner to someone
”If you berate the 4th official, you run the risk of getting a red card.”