Fair play to Huth. Doesn't change the fact that Fellaini was a tit deserving of a red.
My take? In a game like that, the ref has got to call more of the "hard fouls" than he may want or else he loses control. And that may mean calling a PK on a defender during a corner kick. If refs did that a bit more, the play on set pieces may clean up.
No defending Fellaini, he clearly headbutted Shawcross and deserves punishment. However a later event where he lifted his arm and caught him in the neck - the foul there was CLEARLY on Shawcross who had his arms wrapped around Fellaini's chest, HANDS LOCKED TOGETHER. He was just trying to wriggle out of a bearhug (which if shawcross's arms are under fellaini's, that means Fellaini's arms CAN'T be "down" by his side. When defenders are allowed to do that and get away with it, no wonder a player feels they may need to bend the rules as well. The stuff defenders are allowed to get away with on a corner is appalling. It's like the normal rules of the game don't apply until a corner kick hits the ground because the refs would have to call so many PKs...