Don't read this as excusing what he did, but think. Your upbringing was likely night and day compared to Mixon. You got angry enough to pull your fist back. You weren't an 18 year old kid.
He was 100% wrong, but again, look at the circumstance. Blondie didn't like Mixon hitting on her. She taunted him. He lunged at her. She slapped him. He decked her. Its a very unfortunate escalation that he should be above, but he wasn't. He seems to have learned a lesson. Maybe he is a complete punk and has put on a good act since, but I believe he is a normal kid who did something incredibly stupid. I wouldn't be heartbroken if we grabbed him at the end of the 2nd or 3rd.