Cory and I traded emails about this ruling, and here are his thoughts:
The judge ruled on the law the guy was accused of violating, which is a very narrow statute, and the guy was not guilty of violating the statute under which he was charged. The judge even told the prosecutor that this was the wrong statute to be using. The prosecutor -- for whatever reason -- stuck to his guns. Now because of double jeopardy, the guy gets away with it.
My guess is that the prosecutor chose to prosecute under the statute because it carried a higher penalty, and thought that he could intimidate the accused into settling with the threat of a much longer sentence. Instead, this backfired on him. But that's not the defense attorney's fault (his job is to represent his client), and it's not the judge's fault (his job is to rule on questions of law). It's not even the law's fault (there are statutes under which this guy is clearly guilty, but those weren't the statutes used in the case) Sounds like it's the prosecutor's fault for trying to shortcut the trial with a quick plea through a bogus charge.
I guess the point is that it's a different kind of problem: this isn't a case where society can't tell the difference between "legitimate rape" and some other kind of rape. It seems like the judge would have been happy to lock this guy up, if the prosecutor had charged him with the crime he'd actually committed, and it's probably good that judges aren't willing to convict people of crimes they haven't committed.