I read the whole transcript (all 72 pages) and those Justices were all over the place. One moment they're going against the guy trying to push the law saying that video games are no different than violent movies or cartoons, the next minute they're going against the guy pushing for the law to be hammered down by stating that the Founding Fathers could never have foreseen video games when forging the 1st Amendment 200 years ago.
I would agree with them that California's proposed law is so vague in it's points that it could cause a judicial run-over onto other media forms such as movies, television, books, comics, and more.
The prominent argument with this law is that it help parents that "aren't always there to raise their kids", so it helps to keep (deviant) violent materials out of those kids' hands. Although it's rather clear by going into any Gamestop or Walmart when trying to buy these games, that the independent ESRB is already doing a great job on that already. And, the fact that parents are not raising their kids and instead rely on the government to do so should not be faulted on the video game industry, but instead put to blame exactly on those parents.
Eventually this mass-censorship will cause us to enter an Equilibrium (http://www.imdb.com/title/tt0238380/) state of control, which is not what we want.
P.S. Under the events of Columbine, a large group of parents blamed DOOM and Marilin Manson for 'corrupting' the two youths that were behind the event. A very little amount fingers points towards the parents, of who's house basement was where the two created bombs, plans, and stockpiled guns. A scapegoat was created because nobody wants to admit that in America's society, the way parents raise their kids as apposed to 50 years ago is going very wrong.