Did you even watch the video? I did. HE INITIATED the argument. In the video, at 0:30, HE WALKS UP TO HER, and apparently says something which enrages her. She shoves him, and he responds by decking her.
A punch from a football player, against someone much smaller, is potentially deadly force, and is an unreasonable escalation against an assault which is not likely to cause him damage. Give her a slap, OK. Punch her in the face and knock her down? Not OK. He needs to go to jail.
This disgusting incident is a teachable moment: Girls, don’t hit people it will get you in trouble....Boys, don’t hit people it will get you in trouble...Young people, don’t get drunk and act like a-holes, bad things happen.