You and I are seeing two different plays because Thompson led with his helmet this the reason his helmet was first to make contact. The fact that you bring the shoulder at all is laughable, as that came after the hit with his helmet, so that is a non-issue here. and
Plus go back slowly over the play, because if Cooks hadn't lowered his helmet, Thompson would have hit Cooks in his face mask, as that is where Thompson aimed his helmet, and Cooks would've ended with at the very least a more severe concussion, and most likely worse than that.
The NFL rules stated if a player is aiming at someone with there helmet and makes contact that is a penalty. I'm going to go even further. That hit by Thompson was dirty.
The shoulder makes no difference, he was aiming his helmet towards Cooks' facemask, but only hitting Cooks helmet when Cooks lowered his head to protect himself. When he lowered his helmet was Cooks aiming to hurt someone? No! Was Thompson aiming his helmet to hurt someone? Yes! That is the kind of tackling coach Csrrol is noted for that he teaches.