You're right in that this was a stupid act that may cost both young men dearly, I have a hard time seeing how the kid the OU player pushed/goaded into action will get much of anything in the way of punishment, nor should he. Once one person puts their hands on another, brandishes a weapon, etc., all bets are off. It's self defense. The MMA kid did not escalate beyond what would be considered reasonable given the fact that the was not the aggressor, could reasonably have said based on the video that he feared for his own safety and was at a size disadvantage.
One of my dad's best bits of advice in my youth on such matters was to 'Be careful. You have no idea who you're dealing with when you meet a stranger. You don't have any idea what he's capable of, what or who he knows.' Another gem was 'Never get in a fight with an ugly man. He's got nothing to lose'.
My two are the both pretty much 'Head down, stay the course' as well, so I'm also thankful.