Ferguson felt Gallas deserved to be red-carded by referee Alan Wiley for a challenge on Nani in the second half.
"He kicked Nani from behind and the referee called both over because they sized each other up. He should have been red-carded."
Wenger said: "Nani was very good today but he did not need to juggle the ball.
"He is a young player and wanted to show what he could do. Maybe he can learn from this."
Ferguson agreed. "I think he shouldn't be doing that, he doesn't need to do that," he said. "In some ways it shows a great deal of courage to do what he did, that's one side of it."