Did you notice in the scene just leading up to the fight he was looking at everyone's muscles? They had closeup shots. Also he spoke about how he was being treated by his associates with his therapist and she said it seems like the alpha male syndrome was in effect. They smelled weakness. They viewed his weakened physical condition as a weakness in his power and judgement. People were plotting a scheming in other episodes. Plus, remember how they all viewed Johnny Sak as a wimp because he cried when in hand cuffs? They thought it could lead to him ratting to the feds! It was a sign of weakness to them. So in order to make it abundantly clear that he (Tony) was not weak physically or in his judgement or his ability to make firm decisions, he beat the living crap out of the guy which made the other guys say wait a minute, Tony is alive and well and he's in charge so I better fall in and fly straight, quit second guessing him and arguing with his decisions(which is what was happening - the scene with Chris at the wedding about whacking the guy for Johnny as a favor). It puts that fear factor back into Tony which leads to a healthy respect for him. Its the mob mentality. You don't want to cross a man like that. Sort of mob office politics. It maintains him as the dominate alpha male.
