The Frenchman was dismissed early in the first half for headbutting Nedum Onuoha after claiming he was pushed by the defender when going in to block QPR goalkeeper Rob Green???s clearance.
Arsenal held on with the 10 men despite a nervy finish, and Wenger cannot complain about Giroud???s subsequent three-match ban for the incident.
Wenger said: ???It was a deserved red card. Madness is a strong word, he did not kill him you know, he touched him and should not have done it.
???He should be in control, he knows he made a mistake but I know him well enough to know he won???t do it again.
Wenger stood up for his striker despite the fact he will miss the important clashes over the new year period at West Ham and Southampton, as well as the FA Cup visit of Hull.
Giroud???s compatriot suggested the reaction may have been triggered by a concern about picking up another injury having only recently returned from a lengthy absence for a broken tibia.
???He told me he was pushed in the back and projected against the ???keeper,??? Wenger said. “Maybe because the injury he had it plays a part in his mind and he doesn???t want to be injured again.
???Usually he is in control of his response.???
Despite scoring and assisting a goal and picking up the man of the match award, Alexis Sanchez???s earlier missed a penalty for the Gunners at the Emirates Stadium.
With this, Wenger made it clear that Spanish midfielder Santi Cazorla is the designated penalty taker for Arsenal.
He said: ???Cazorla is number one taker at the moment.???