Hi,
Expressing anger is not necessarily sinful. Anger is an honest emotion. Emotions are like auxiliary generators. They add thrust to our choices, but are not capable of choosing.
If we sin when we are angry it is because of the choice our intellect and judgment have made—not because of the emotion itself.
He may have been angry every time he encountered such inappropriate behavior–if He indeed encountered such before. We simply do not know. But He evidently chose this as a teaching moment and His emotion made an impression that He couldn’t have made without it. Note that He controlled and used His emotion; His emotion did not control Him. We know for sure, He didn’t sin!
Fr. Vincent Serpa, O.P.