Lionel Messi wasn't too happy when both Arbeloa and Xabi slapped him across the face. Sure, they didn't slap him too hard or anything. They sort of just put their hand across his face.
But the gesture was clear: just calm down Messi, we don't think you're all that. It was a dismissive and demeaning gesture. Almost like how their coach, Jose Mourinho, put his finger in the eye of Tito Vilanova last year. Messi's reaction to referee was what are these guys doing touching my face like that.