It's possible that Rottenborn was so pissy about people audibly being against Amber in the gallery yesterday that he made it his mission to go after DUIguy but it's hard to say IMO. There's not actually anything wrong with the gallery reacting as long as they're not disruptive, and he was by no means alone in his reaction - which the court would see better than people watching a film of it.
Personally, I think it's too early to tell. DUIGuy claims that nobody minded yesterday, despite POGface being the day before and him not doing anything untoward yesterday. It's easy to assume that he's been singled out because of the Bytes drama happening right before that...but coincidence is coincidence. If they don't allow line-cutting via scalpers, then it is entirely possible that he just got caught this time and never before. It's also possible they paid attention to him this time because he stuck out and that's why they caught him, which is an in-between.
Looks like prepping excuses for when Amber gets destroyed by the jury, to me. If Amber's got such a compelling and powerful case and the jury believes her they'd actually be turned against Johnny for this.