The player will likely be ruined,and deservers it for losing control, but I have absolutely no sympathy for these fans. None. They're bullies and drunken thugs, and bullies usually end up with bloody noses when they run across somebody who won't put up with their crap.
I don't really care in what sort of behavior the fans engaged. If they were over the line, the stadium folks should do something about it. It's beside the point.
The point is that physical violence is an order of magnitude beyond verbal abuse. Physical violence with a metal chair is a couple of orders of magnitude beyond verbal abuse.
If the couple were (seriously) threatening physical violence, then they themselves committed simple assault. If the player had real reason to fear for his safety, or that of his family, etc., a physical reaction could have been justified. The jackass who confronted Yankees players INSIDE THEIR OWN BULLPEN last year deserved the light beating he took. His behavior had moved from extremely abusive to physically threatening.
But potentially deadly assault is never justified as a response for verbal abuse.
Furthermore, these players are paid ludicrous amounts of money to play a game. Their position is one of great, unimaginable privilege. The yawning chasm between the players and the fans mitigates abuse offered by the fans. These players are paid better than Superman. They'd best be better than Superman. If they aren't, then they need to give back the money, or get the hell out of the game.