Gus Poyet defended Oxfordshire referee Graham Scott after he sent off striker Dave Kitson in Pompey's FA Cup defeat at the Withdean.
The Brighton boss, who celebrated a 3-1 third-round triumph, described it as a 'very strong early decision' but believed it was correct.
The former Chelsea midfielder also conceded the red card made the Seagulls' task much simpler.
He said: 'The sending off made it easier and it was the right decision.
'It's too easy to blame the referee.
'The idea was to compete 11 v 11 for 90 minutes against a Championship club in a beautiful competition.
'In the end we totally deserved to win.
'This was a game we dominated from start to finish.'
Brighton will now travel to Watford in the fourth round.