Oxford boss Chris Wilder accused Barnet's Sam Deering of getting U's skipper Jake Wright sent off in their 2-0 win over the Bees.
Simon Heslop and Liam Davis both struck before the break to put Oxford in control and, though in-form Izale McLeod flashed a second-half header over, they always looked comfortable.
However, Wilder felt the shine had been taken off the win by the dismissal of Wright, who collected a second yellow card for a stoppage-time foul on ex-Oxford man Deering.
"I just don't think he had to roll around," he said. "He wasn't hurt badly and they were trying to win the game.
"He rolled around five or six times and I'm just glad he didn't roll towards our supporters. For him to get our captain sent off is a bit offside in my opinion."