I thought it was a good call. The rule 63.6 states....
In the event that the goal post is displaced, either deliberately or accidentally, by a defending player, prior to the puck crossing the goal line between the normal position of the goalposts, the Referee may award a goal.
In order to award a goal in this situation, the goal post must have been displaced by the actions a defending player or goalkeeper, the puck must have been shot (or the player must be in the act of shooting) at the goal prior to the goal post being displaced, and it must be determined that the puck would have entered the net between the normal position of the goal posts.
IMHO, a goal was imminent. The player had position, and he was going to have an easy tap in goal. Smith pushed him into the net and therefore caused the net to be dislodged. It really is a no brainer call in my opinion.