Even though the "fights" were staged, the Duck was just defending the Autzen turf.  The Cougar was trying to do push-ups (after a score) on the game field (two different times), and both times, the Duck ran over and put a stop to it.

The push-up thing at Autzen is a tradition for the Duck mascot to perform.  To have another mascot do them "disrespects" that tradition.  The suspension is only coming now, because of all the local media attention about it.