I can agree with you that he has to be more careful because he did make contact with the helmet and that could be called according to the rule that @TerryP posted. But I still see it as a shove. The guy was riding him pulling his mask, they were moving right and a hard shove to the right makes the guy's momentum take him way right. It looked like a "bitch get off me" shove that made contact with the helmet incidental in my opinion. Only Fournette knows if it was a punch or not. I'll concede that much.
I couldn't be sure if his fist was closed or not. If his fist was closed it was a punch. If his hand was open it was a bitch slap