If fans have the right to do whatever they want to a player in the stands, they shouldn't put the stands so close to the court where someone ends up there a couple times a game. Fans are there to watch the players. The player ended up in the stands after making a basketball play and some assholes took advantage and started heckling him. At that point, Smart reacted.
In your analogy, a fan comes on the court to start crap. A more accurate analogy would be a fan falling on the court from the stands and Smart running up and heckling him.