The author hit the nail on the head with this point.
The only way for Kerry to walk away from this, unscathed, is to publicly chastise the Media Wing of the Democrat Party and the bitter partisans in his own campaign. (Heck, he might have to have the DNC play scapegoat and fire Terry McCauliffe!) MOST IMPORTANTLY, though, he's going to have to steal a play from Bush's playbook, and publicly state that Bush "served honorably".
Anything short of that, and the Dirty Tricks charge will be directed straight at him.
Kerry's response about this smear was, "That's for the White House to answer."