The under-pressure boss saw his team play with pride and passion but the red card obviously gave Boro a thankless task in trying to retrieve the game against Arsene Wenger`s title pretenders.
"I thought we started really well and put them under a bit of pressure," Robson explained.
"I thought it was a harsh decision. `Pally` (Gary Pallister) was getting back behind Mark Crossley so he wasn`t really the last man.
"Things like that go against you when you are on a downward spiral.
"Referees see things in different ways regarding the bigger teams.
"Their first bad challenge was Lee Dixon`s on Andy Campbell. Ours was Mark Summerbell on Patrick Vieira, and he was booked. Decisions go against you like that.
"The penalty was harsh enough - I didn`t see the reason to send our goalkeeper off too. It gave a top team like Arsenal a real grip on the game.
As regards his own future, Robson believes that the crunch games will be the home fixtures with Leicester and Bradford, rather than next week`s daunting trip to Manchester United.
"I`ve got 100% support from the board and I need to get my head down and knuckle in.
"We`ve got two important games at home against Leicester and Bradford. They are must-win games."
When asked about the rumour that Terry Venables will be joining Middlesbrough as a coaching consultant, Robson revealed there was no truth in the reports.
