Dong knew the knee was coming to his temple, he had his hand touchin the floor when Diaz motioned to throw the knee and obviously it's going to be a knee-jerk reaction to lift your hand up when someone is kneeing u in the face. Was still technically a foul IMO even tho his finger probly was a millimetre from the floor when the knee landed. Nonetheless, as Rogan said it's a stupid rule anyway.