Farrell was originally penalised by referee Steve Walsh for reacting to Brits’ indiscretion but Walsh reversed his decision on viewing television replays.
Brits received a yellow card, spending ten minutes out of the action as the Lions powered to a 59-8 victory, scoring eight tries.
Lions head coach Warren Gatland said: “It was just a ruck situation. Owen is holding on to his jersey, Brits has got a bit frustrated and let fly. The good thing was that Owen wasn’t injured or knocked out. I was pleased he [Brits] wasn’t sent off, and just given a yellow card. Had they played with 14 men it would have been less of a hit-out for us.
“Sometimes it is hard when someone lays a punch squarely on the side of your jaw not to react. We are going to emphasise from the start of this tour the importance of keeping our discipline.”
Wales scrum-half Mike Phillips inspired the Lions to a comprehensive triumph at hot and humid Hong Kong Stadium.
Phillips, the Lions’ most consistent performer, scored two tries, while wing Alex Cuthbert also claimed a double and there were further touchdowns for skipper Paul O’Connell, centre Jonathan Davies, flanker Dan Lydiate and substitute Alun-Wyn Jones. Farrell kicked 15 points, but he had a mixed bag of a game elsewhere, making some poor decisions, with one handling blunder leading directly to a Barbarians try. His replacement Jonathan Sexton added two conversions. Gatland added: “I think the scoreline reflected our dominance in the end. I was generally very pleased. It was tough out there. The players said the ball was like a bar of soap, with the humidity and heat.
“There is no-one unhappy in terms of the performance. I thought our control was excellent and our kicking strategy was pretty good. We can’t complain.
“Going forward, the players who played today have laid down a marker. It was about us putting some foundations in place.”
O’Connell, who took charge while tour skipper Sam Warburton continues his recovery from a knee injury, described conditions as the toughest he has known.
“It was incredibly difficult, the most difficult conditions I have ever played in. It was just hard to recover during the game,” he said. “You just wanted to get into it. So, from that point of view, the tour really starts and takes off from here. We did a lot of good stuff.”
Barbarians coach David Young described the Brits incident as “unfortunate” after his team suffered another drubbing just six days after a 40-12 defeat against England at Twickenham.
“You don’t want to see any incidents other than the rugby,” Young said. “He [Brits] was being held back and couldn’t get into the defensive line, and he lashed out. You are not going to say that’s right, but that is pretty much what happened.”
The Baa-baas managed a consolation try from replacement scrum-half Kahn Fotuali’i, but Young admitted there was little they could do after being starved of possession.
“The Lions were very efficient,” he added. “I would have thought they will feel there is still room for improvement, but they certainly starved us of possession, both at lineout and scrum.
“We were tackling for large parts of the game, and that was always going to sap our energy but I thought our commitment was far better than it was against England.
“I am really excited and looking forward to every game in Australia. I expect a Lions [series] victory – I think they have got too much strength in depth. Competition for places is going to be huge, and that is only going to push up the performances.
“Speaking to the Lions players today, they feel they benefited from the experience. It gave them an opportunity to have a real hit-out. From a rugby point of view, I see all positives.”
And Baa-baas captain Sergio Parisse said: “It was the first time I have played in this humidity. It was difficult to run, but that is no excuse, it was the same for both teams.
“It was difficult to manage the ball and put passes together, it was difficult to catch the ball and make good spin passes, and the jerseys were really wet so it was difficult to keep the ball.
“The Lions have a lot of skills, and I think they can win every game against Australia.”