They're saying the same stuff they normally say. Timing is "too" convenient. It's planted. Al Qaeda brought it in, etc. No one admits it could be from Iraq. After all, if there were WMD's found in Iraq then the US would be vindicated in the eyes of the world...and the Lefties can't have that! Draws away from their plans to turn over sovereignty to the UN.
I think I know what they'll say: "Sure, it definately happened, but this is just an isolated incident, not evidence of anything systematic or widespread". Naturally applying the same logic to Abu Ghraib for them results in a totally different conclusion: "Of course it's systematic...", etc....
Oh the irony... though I doubt Kerry can appreciate it. If it wasn't so shameful, it would almost be funny that Kerry et. al. think Saddam incapable of any evil, and think our troops capable only of evil.