Offside isn't interpretative, handball is. Not a good comparison. As I said it is factual that Tadic was in an offside position. There really isn't anything to debate over or discuss in that situation.
You're oversimplifying, because passive offside is 100% interpretative.
You can stand offside all you want if you don't make an attempt on the ball, or impede the keeper's ability to make a save. In this case, I don't believe the player impeded the keeper to the point that it warranted the offside call. You're welcome to think it did, but let's not act like it's unbelievable that someone doesn't agree with you.
Anyways, water under the bridge now. It was disallowed.