Gallas backed shamed striker Emmanuel Adebayor after his red card and said his team-mate's face spoke volumes in the visitors' dressing room after the game.
The Frenchman said: "Even if he didn't say anything, he was really, really sorry. We could see that on his face. Now we have to forget that game because it was painful."
Like Adebayor, Gallas is a former Gunner who now comes in for stick at the Emirates.
He said: "You have to keep everything inside. I know it's not easy, especially when you come back to the Emirates. The fans boo you but you have to be strong."