I know what I'm supposed to say about this Kerry thing, but sorry -- whatever he meant to say, he walked into an ambush, and he has to get himself (and, by extension, the Democrats who are actually running this year) out of it.
Don't think like a Democrat or a progressive; don't look at the poll numbers and assume that every person who's against the war is going to pump a fist gratefully because Kerry lashed out after being attacked. Hey, I like his piss and vinegar, too (where the hell was it two years ago?), but it doesn't matter. This has been declared An Incident, and it has to be neutralized.
It doesn't matter what he meant. It doesn't matter how a Republican would have been treated if he or she had said the same thing. It doesn't matter, in other words, whether this is fair. All that matters is what's actually happening. Kerry has to grit his teeth and accept it, then deal with it, for the good of the party. And if you can name a hundred more outrageous -- and deliberately outrageous -- things Republicans have said that passed without incident, well, reversing that imbalance is a long-term project. For now, Kerry has to show some contrition, in a conspicuous way that will put an end to this.
Then he can lash out at Bush. And I hope he does so again, and is even nastier.
UPDATE: Via darms in comments, I see that Kerry talked about this on Don Imus's show this morning. Here's the transcript -- he apologized, and he also got in a few more jabs at the administration. My thoughts are here.