The fact that he didn't spend pages talking about it is not the issue, but that he didn't when there's a large amount of case law that interprets the anti-circumvention clause of the DMCA completely differently. The second update to the story provides a more likely reasoning for the lack of analysis:
"Update: New York Law School's James Grimmelmann emails to suggest an alternative explanation or the shortness of the judge's DMCA analysis. He notes that the plaintiffs focused their arguments on the trafficking provisions of the DMCA, but ignored the circumvention provisions. Since the plaintiffs didn't raise the circumvention issue, Judge Marshall didn't need to address it. He dismissed the lawsuit without prejudice, so Ambrose can amend its complaint and try again."
The problem with a ruling like that is that, by not addressing the existing rulings, it limits the value of an otherwise good precedent. If you don't address an issue, legal types usually assume that you cannot, so it's a good way to lose that part of the argument. If you've read enough legal briefs, you will no doubt have noticed how many times they call each other out for failing to argue something or another. Parties in a lawsuit who don't raise some important issue or say what they're supposed to generally don't get another chance to do so, which is how we end up with crazy boilerplate that tries to cover every little thing.
That said, I'm glad this judge did the sensible thing.
Did you read the sentence almost immediately before that?
"We've never liked the DMCA's anti-circumvention language, so we'd be delighted to see the rest of the judiciary agree with Judge Marshall."
I don't think it's insulting, but rather that the author thinks others might interpret the judge's ruling as one that he didn't do his homework. Now, if the judge had written a larger report specifying exactly why the ruling stands in great detail, this ruling would have been a bigger precedent and not something that is just about DVD ripping and not against the whole DMCA anti-circumvention.
Wow, a judge rules correctly, and because he didn't spend pages talking about your pet subject, he's an idiot?
Cripes, no wonder we can't make headway against DRM if zealots insult everyone who isn't a zealot.