For some here who don't understand the rule applying for the play in the game, targeting is defined as "leading with the crown of the helmet while making forcible contact, or making forcible contact with the head or neck area of a defenseless opponent with the helmet".
Defenseless is defined for many situations, but for the play in our game it says "A player with the ball who is already in the grasp of an opponent and whose forward progress has been stopped". He was ruled still moving forward.
See official rule book (Rule 9-6) (A.R. 9-1-3-I)