I have no problem with DaJuan Gordon stealing the ball with 3 sec to go. They've been beaten by 20, if he wants to show he's a fighter then go for it. It's one thing for a winning team to keep from padding the score in a decided game, it's another for a losing team to try to show they have some heart at least instead of losing interest because you've been thrashed.
Da Silva was also right to block the shot. The issue was when he decided to stand over the dude like he was some UFC fighter. You've won by 20, you blocked the dude after he stole the ball from you, no need to stand over him and humiliate him further.
Obviously it escalated after that, with some pushing and shoving into the disabled seats, but up till that point it was still a typical brawl until De Silva decided to pick up a chair. Someone could've been really hurt, not just players, but fans who were all caught up in it.