I'm a little late to the thread...but I'll add that while I despise the Seahawks as much as anyone else here....
As much as that was obviously a penalty, I look at the intent of the play or how it would have affected the outcome. He wasn't knocking it out to keep them from recovering the ball.
Ball was going out anyway. No chance Detroit recovers it. Wagner could have just easily grabbed it.
Dumb play because it was a penalty and it could have cost them the game technically. But if they reversed it and got the call right, by the letter of the law, Seattle would have lost on a technicality.
That loss is on Johnson for fumbling.
Boy, is Seattle's offense not looking too good. And their defense, while still good, is far from invincible...can be exploited. I believe they are the 3rd best team in the division.