I don't think its that easy of a thing to call in real time the refs don't get to discuss these. They are going to be paying more attention to the ball handler.
I remember talking to a MWC official who was off duty that night (actually at the Nevada game 2 years ago I referenced in the other thread) and he told me its one of the toughest calls to make and one they often want back when rewatching on replay.
Remember that the defender has nothing to lose apart from dealing with the collision. If you contest the dunk your likely to give up free throws at the very least and also highly likely to give up an and 1. The guy probably won't finish through the charge. High reward since you get a turnover if you pull it off (no chance for an offensive rebound off a miss.)