For the umpteenth time, the "Iron Clad" contract has really only stated that Show can't be fired and that he can take time off whenever he wants (I think, I try not to remember any storyline involving Johnny Ace). Let's say Show decided to talk smack against the Corporation and even starts physically attacking them (because he can). He would then proceed to get his ass kicked by Orton, HHH and The Shield and would be punished and humiliated every show until he either retires or the Corporation dies down. Show would gain nothing by being the only guy (sans Bryan) who is actually willing to confront the Corporation. There is no contradiction or loophole with the Iron Clad contract because there has been nothing (to my knowledge) to indicate that Show is free from any and all punishments, just that he can't be fired. Well he can still be beat up, put in handicap matches, not even used on the show, banned from the arena, forced to wear a dress, etc. anything but be fired. It would just be the Corporation's goal to make him quit at that point.
Yeah it would be nice if maybe HHH or someone alluded to the fact that Big Show can't be fired for speaking up like everyone else, so he'll be punished separately, but it's still not a hole in the story.