After firing the home side in front on 11 minutes, Barton then lost his cool following a tussle with Johnson, when he appeared to headbutt the Norwich midfielder.
After consultation with the assistant, he was shown a red card by referee Neil Swarbrick.
However, the QPR captain defended himself on Twitter, saying: "Well feel for the officials, they've been conned. Admitted to me at HT they never saw it. I was pulled back 1st, then kicked 2nd.
"Linesman definitely never saw it, all he seen was Johnsons reaction. My head dosent move forward at all. Ridiculous decision seen 25 replays."
Anthony Pilkington drew Norwich level just before half-time with a fine 20-yard effort, before substitute Steve Morison completed the turnaround with eight minutes left.
Barton continued his defence on the social networking site, adding: "I'd be 1st to apologise if I'd reacted. Cannot apologise as I know I've not head butted anyone. Disappointed for the lads and the fans.
"Make ur own minds up when u see it. The games gone!"
Barton called for the incident to be reviewed. He added: "Hopefully referee sees it retrospectively and sees he's been conned. Its no consolation for us right now but at least its something."
Paul Lambert maintained he did not see the incident, preferring to instead focus on his own team's efforts.
The Norwich manager said: "I thought the lads deserved to win the game.
"We started really well and got a foothold, then QPR scored against the run of play, but we kept on going.
"It is relentless, but we have coped brilliantly to this time."
The Canaries were promoted behind QPR from the npower Championship last season, and have exceeded all expectations to sit comfortably in mid-table.
Lambert knows there are plenty more challenges ahead over the next five months.
"The lads have been great, they seem a really close group and we are all in together," the Norwich manager said.
"We will take one game at a time now, and if this club survives in its first year, it will be monumental for us."
Neil Warnock backed his captain and condemned the reaction of Johnson. The QPR manager said: "He has not been headbutted at all, not in a million years. The movement of him going backwards has conned the referee.
"To go back like he did was a disgrace. It's getting a fellow pro sent off. I think he should be done (punished)."
Warnock added: "Joey could have avoided the situation, but it doesn't warrant the reaction from Johnson.
"I think we have been mugged. The ref has not even seen it."
Warnock will wait to consider whether the club will appeal to the Football Association against what is set to be a three-match ban for Barton.
He said: "When [Wolves manager] Mick McCarthy appeals and does not get that lad [Nenad Milijas] off, you have got to worry about anything appealing.
"I have not got any confidence in the appeals procedure.
"We will have to look and see what the referee says [in his report] and if there are any other angles, but from every one I have seen, I don't see a headbutt.
"But I am not optimistic. We will have to decide later."
The defeat was an eighth in the last 11 for Rangers, who are hovering just outside the relegation zone.
Warnock named on-loan Manchester United striker Federico Macheda among the substitutes and is expected to do more business in the January transfer window.
The QPR manager said: "We should be positive, the lads have been fantastic.
"We will regroup, hopefully get a couple of players and then look forward to the second half of the season.
"I think we should be 10th or 11th with the chances we have had and a bit of the rub of the green in the last few weeks."