As per the rule book, you're allowed to touch. It's only a penalty if there's any twisting/turning of the helmet/players head. If you break it down, yeah you can make an argument that he just touched but that's only if you slow it down. At full speed, it looked worse than it really was. You can't fault the referee for something he can only judge based on real-time/game speed.
Everyone complaining has the luxury of various views and instant replays thinking it's easy to make that call on the field. Don't blame the referees because I bet if any of us were there on the field, we'd call that 9/10 times.