Referee Walton had no hesitation in producing the red card to the Ivory Coast international but Wenger insists that the decision was incorrect, hinting that the club may launch an appeal.
"I don't understand the red card. I am 100% sure the referee did not see what happened," Wenger told reporters after the final whistle.
"I think he had his back turned to the incident. If he had seen it, he would have sent both of them off, or nobody.
"Will I appeal? I will have a good look at it but I am tempted to say yes."
Hosts Newcastle were unable to make their numerical advantage count as the game ended in a 0-0 draw.