There is no way Hoffs goal could have been any kind of foul. He jumped at the ball, put his head to where the ball was supposed to be, didn't use his hands or his body to gain any advantage. Just jumped.
The fact that he hit the keepers hands is irrelevant. if it was another players head (not the keeper) it would have stood and been see as an accidental head clash within the moment, "a part of the game" if you like.
We place too much protection around the keepers at all times, when the only time we should be protecting them more is when they're on the ground around swinging feet/legs.