Prudence is a guilty plea? Tell you what, don't need to hire a lawyer at all, everyone knows you hire a good lawyer to avoid jail, not because you're innocent. If he wants to avoid looking guilty he should represent himself.
Being stupid doesn't prove you're innocent, it attracted attention so it's not going away, the guy got injured so there's no way this doesn't end up in front of a judge, and regardless of legal trouble the guy is missing work because of injuries he sustained after being attacked and has bills to cover as is.
This is why lawyers and judges are paid to interpret laws and events. The hostility is still present, he's doing nothing to restrain his friend who already attacked this guy when his back was turned and he's coming off as aggressive himself. If you've ever de-escalated a situation or broken up a fight this isn't how is done. You don't allow one party to continue shocking the other while taking the non-aggressor to get out while threatening his personal space. This dude was left with two options, fight out trust in the face of events to this point that you can walk away without getting assaulted again! Tone, demeaner and behavior prior to the attack shows two people who are acting aggressively, adding to conflict and two who are calmly trying to end the conflict until it seemed walking away wasn't going to be an option. Self defense extends until a threat is over and only over the force necessary to end it. It started with an adult, there was no attempt to de-escalate and he continued to fight back, so the MMA guy has the right to fight until he is no longer in danger. You can't determine a broken bone is excessive because we have no idea when he gained it, but we do know he presented a United front with his friend that was an aggressor, still making personal contact moments before the retaliation and failing to surrender on the ground. It's open to interpretation but you don't get to say no reasonable person could believe his actions necessary, it needs to be interpreted in the courthouse, the only appropriate place for that because it's the best system for that. Everything else is your prejudice (legal sense not racial) and I doubt you'd so readily disregard due process if you were up for something.