The ref that had it 29-28 Sterling should be fired.
In this situation the belt should be taken away but not awarded to Sterling since he was losing a majority of the scorecards. The belt should be vacant until a rematch. If Sterling was winning the majority of the scorecards then he would be awarded the belt.
Lost in all this is how stupid it is to even disallow knees like that. If you allowed them then you wouldn't see fighters stay in those awkward positions as much. Fighters would be aware it's a very vulnerable spot and avoid it to begin with.