Yeah Kos was at fault. but it could have easily gone another direction and whats to say Gibbs could have been the guy who did not mark it well.
Yes Kos should have defedning better, but if your going to give cynical fouls, then don't do it near your boxm do it near the halfway line.
Maybe Arteta should have bought his man down before it got to that stage.
Bould would have had faith in Kos, and as he has been teaching the boys how to defend im guessing Kos would have got a boot in the head.