Robinson believes Smith was shown the red card because of his reputation rather than the aerial challenge with Rory Delap.
"I didn't even know it was a foul," he said.
"But you see Alan Smith going to try and compete and right away ultimately the referee thinks 'that's Alan Smith, he has tried to do him, sending off'.
"You could see it and, by the way, how quick did he go for his card? It looked like he couldn't wait to do it but if he sticks to his report he will know he has made a big error."
Robinson added: "I thought in the first half we were poor.
"We were as bad as we have been but the second half was more like us, tried to retain the ball and play the game right.
"It was a very split game, they were the better team in the first half and we were better in the second half."