When you look at this, are you 100% certain that contact is within 6 inches of the top? I'm not. And there isn't a definitive angle—I didn't see a broadcast angle that showed the other side (looking over the ASU WR and toward the Texas DB), so that's all the refs had to go on...
I think you have to be completely certain when you're ejecting someone, especially in a situation like that (where a penalty there gives the game to ASU).