It almost seems like this public defender just snaps. You see him standing to the side of the podium next to the defendant, when he aggressively tells the judge he won't waive his client's right to a speedy trial, unprovoked.
The public defender then says the judge can do whatever he wants, whether that means a trial or set it for a docket, but he, the public defender, won't wait. (He delivers all of this in a very disrespectful tone.)
You can't see the judge, but you can tell from the silence following those statements that the judge must be seething. Finally, the judge tells the public defender he'd like to "throw a rock" at his head, and things rapidly go downhill from there.
At :47, you hear the ultimatum about wanting to fight, then you see the public defender abandon the defendant, who he leaves standing in utter confusion at the podium, to quickly walk toward the bench.
The public defender disappears from view and at :57, you hear the sounds of a scuffle. Finally, at 1:38, the judge reclaims his seat and receives a standing ovation from the people in the courtroom.
(WARNING: NSFW audio during the fight...you can hear a couple f-bombs thrown in there from what sounds like the judge.)