Nearly every statement in your post is incorrect. Congrats. One at a time:
A proper form tackle does not mean driving your facemask through a player's numbers.
A proper form tackle involves approach, contact and wrapup. Since Chung's approach was amazing and wrapup wasn't overly important in this case, focus on the impact. There isn't a single correct way to initiate contact on a tackle since it depends on a variety of factors...size differential, approach angle, situation (first down, goal line, etc). The primary consideration for Chung was speed and the ability to close the distance in the minimum amount of time. Shortest distance = straight line. Chung wasn't just trying to tackle Henne...he was trying to disrupt the pass. The situation would have been totally different if Henne were scrambling. So in this case, the situation called for Chung to put his body (facemask leading the way) into the closest legal point on Henne's body in the least amount of time.
Facemask goes on whichever side the ball is being carried on in order to gain control of the runner
This works well against slow, small running backs. Unfortunately you don't see many of them. Adjust to the ball side of Reggie Bush and you won't have to worry about drawing a penalty. You probably will have to hustle back for the extra point after you whiff on the tackle. Try that on Brandon Jacobs and the only question will be how far you bounce off him.
Primary force should come from the backside shoulder pad.
That only works if you have a reasonable momentum (mass x velocity) advantage. You are depending on the force of the contact to do most of the work for you. Your center of gravity is offset from the opposing player's center of gravity. If you don't knock them out with the contact, a side step or spin move can free up the runner to continue. Also, it is more difficult to wrap up after contact if you are offset against the runner.
The helmet should slide off to the side during the course of the hit,
Unless you are Steve Grogan or Merton Hanks, the location of your head doesn't stray too far from the center of your chest. If your head slides off to the side, the rest of your core will tend to follow.
not piledrive the runner into the ground.
That is a post-tackle action, which is why it is called as unnecessary roughness. In no way did Chung piledrive Henne and it doesn't necessarily follow that a hit like Chung's leads to anything like a piledriving motion. That takes additional effort and intent.
Chung's primary force came from the contact he made with his facemask.
Seriously? What is Chung's neck made out of? I will wager Henne barely moved until Chung's core made contact. In fact, the penalty would never have happened if your scenario were true. Chung's head was well below Henne's facemask at initial contact. Since Chung's head/helmet didn't have enough force (mass x acceleration) to move Henne, it slide upward as Chung's body kept moving forward.
The facemask is there to protect players from such hits, which frequently occur when the tackler misjudges the tackle, but that is not a classic form tackle.
This is just silly and your attempt to phrase it with such certainty makes it even worse. There are any number of other more important reasons for facemasks beyond "poor form" tackles. Blocking, incidental contact in pileups, just hitting the ground.
